Reaction (anagram contained in conversation)
+++++
One time I dropped my ice cream cone (4)
ONCE (anagram of cone)
++++
A headless robot played with a book of cards.(6,4)
Incorrect. Plus, your answer doesn’t start with the correct letters.
I’ll accept that it might not be the solution you were thinking of, but it is a solution and it starts with a perfectly cromulent overlap (R)
What’s the wordplay and definition you used to come up with your solution.
For definition, I thought “easily angered” could be construed as a reaction. For word play, I thought “in” was signaling the solution was contained in “conversation”, and that “only temporary” (i.e. not for all time) meant the solution did not use all the letters. I thought it was a very clever puzzle, but apparently my interpretation is not what you were intending.
That being so, I yield to the thread that my solution is incorrect, and therefore HF’s puzzle is still in play. And while I still don’t know what the correct solution is, I think I can offer a hint: It doesn’t start with R.
ERASABLE (double definition)
+++++
One terribly long time (3)
EON (anagram)
+++++
This bridges the gap between ERASABLE and ONCE.
Which brings us to Skunkdog’s:
+++++
A headless robot played with a book of cards.(6,4)
(Answer to which… I have none yet.)
Correct answer, but the wordplay I was going for is IRASCIBLE (being easily angered) “in conversation” (i.e. sounds like) ERASABLE
Huh? Erasable and irascible don’t sound much alike by me. Would anyone mistake one for the other “in conversation”? Doubt it.
Nevertheless, headless robot?!? We need a hint, else the thread is stalled.
It’s a double meaning clue. Here’s the split.
A headless robot played / with a book of cards.(6,4)
The last part of the clue isn’t necessarily grammatically correct. Hope that helped.
The single difference in pronunciation is the former has a long ‘a’ sound and the latter a short ‘a’ sound.
I’d say that’s pretty close for sound alike. Cryptics don’t require perfect homophones.
Point taken. I didn’t mean it to come across as critical; more like bustin’ chops 
Gotta do something to pass the time while we wait for another headless robot hint.
To that end, I’ve always pronounced erase with a long e at the start, but this prompted me to look it up, and the unanimous consensus of three online dictionaries has a doggone upside down e as the first sound! Ylsned.
dealer boot?
ndroid deck?
Wow! Thought someone would have gotten this on day one. Let me try again.
Headless TV robot played / with a book of Card’s.(6,4)
Ender’s Game?
That’s got to be it. I have never heard of robot “Bender” but that name shows up when I google “Fifty famous robots.”
While we are waiting let me tell you that this month’s Harper’s cryptic puzzle “Terminology” is an absolute BEAST and so rewarding to complete.
This month’s GAMES left out their two regular cryptics. They at least kept the usual two variety cryptics. I was bummed.
I have not cracked my latest GAMES copy yet. Sorry to hear they cut the non-variety cryptics!
I have not downloaded any of the recent Cox/Rathvon puzzles from WSJ this year. Looking forward to a later vacation to catch up on all these puzzles.