Clair IS an underaged girl, but she’s not an object of lust! She’s Raymond* (“Gilbert”) O’Sullivan’s little niece, and the song is about how simultaneously cute and exasperating a little girl can be to a man who’s trying to babysit for her.
*His real name was Raymond, which is why Clair calls him “Uncle Ray.”
Hot Child in the City - Nick Gilder
“She was just seventeen”
The age of consent in Britain is 16. She’s of age by a year or more.
Clair does not “allude to/celebrate or otherwise embody previous generations’ fascination with the sexual allure of underage girls”. It’s about babysitting his manager’s toddler.
Depeche Mode - Question of Time, about a 15 year old.
ABBA: Dancing Queen
Winger: She’s only 17.
And BTW, curse you OP for making me think about Winger! 
This is the first song that came to me. 
God bless you always!!!
Holly
Even this understates by a mile. Back in the 1950s, rock ‘n’ roll was expected to be consumed by teenagers, high schoolers. If they went on to college they were assumed to graduate into “adult” music. Songwriters pitched their lyrics to their prime audience and sixteen was the sweet spot.
The audience for lyrics about sixteen year olds was primarily sixteen year old girls. The guys got into it, too, but the consumer were the girls screaming at an Elvis concert. The songs had this delicious undercurrent of sex, but they weren’t about sex, or at least they were no more about sex than they were about crushes, romance, kissing, longing, drawing hearts in notebooks, and unspecified hormonal rages. That’s because the boy on the other end of these lyrics was also supposed to be sixteen. You don’t have underage sex between high school lovers. And even if the girls did daydream about the older men singing the songs, they were doing so in a time when the average age of first marriage was 20, the lowest it’s been in U.S. history. Marriages were legal at 14, 13, even 12 under some circumstances.
I can’t pinpoint when the concept of being underage became a big deal, but it was definitely post-Beatles. Playboy had a number of seventeen-year-old Playmates and the January 1958 issue featured a student named Elizabeth Ann Roberts who was still sixteen. Her mother accompanied her and signed permission. The laws about drawing the line at sexual imagery at 18 were passed as late as 1967. It’s hard to argue that the totally demure shots of Roberts that are all over the Internet qualify any more than the topless shots of seventeen-year-old Thora Birch do in American Beauty.
It’s weird having this huge cultural change take place entirely in my adult lifetime.
“Louis Quatorze” by Bow Wow Wow
the SDMB rules! thanks to everyone, keep 'em coming… I think we have a new convert, so hopefully we will hear from the Prof himself…
“Wrong Way” by Sublime is about a 14-year-old hooker.
Not to mention that McCartney was only 18-19 himself when he wrote it.
Kiss – Christine Sixteen
Fleetwood Mac – Edge of Seventeen
Friend of the Devil by The Grateful Dead, which has the line “…second one was prison bait, the sherriff’s on my tail, and if he catches up with me I’ll spend my life in jail”
According to a Google Ngram, “jailbait” appeared around 1940, but didn’t really take off until the late '60s.
On the other hand, Jerry Lee Lewis wrecked his career in the late '50s by marrying a 13-year-old.
Sixteen Candles, by The Crests
Oh, did he have a problem?
My first thought on hearing the question in the OP was: “Let’s check the Gary Glitter catalog.”
You see jailbait used on some of the sleaze paperbacks of the 1950s, but it definitely wasn’t a mainstream term.
But it gives me an excuse to quote Andre Williams’ 1957 song, “Jail Bait”.
A 13-year-old first cousin. It was the first cousin part that was ruinous, something that is blinked at today and legal in most states.
And if you’re married, it ain’t jailbait. Gotta love hypocrisy.
Frank Zappa’s “Magdalena” must be included on this list.
Interesting song in that it features Mark Volman and Howard Kaylan delivering virtuoso vocal performances of some of Zappa’s most reprehensible lyrics. (Lecherous man soliciting sex [unsuccessfully] from his teenage daughter.) The girl is “teenage” so whether or not she’s legally underage is unclear. But still.