GASTROPUB (anagram of “a grub stop”, nice one - I particularly like anagrams that also serve as the definition)
+++++
Give up in dubiously headless way - it’s all over (12)
Ubiquitously (dubiously - d + quit (inserted))
++++
Poem about 50-yr. icy relationship (5)
LYRIC (L = 50, + yr +ic)
+++++
Ay, ay, ay! Now is the winter of our discontent very nearly over, Dick. (7,3)
Richard III (three)
+++
For the third time my pee is interrupted in the theater.(5-4)
RICHARD III (Dick + I,I,I)
Noisy North Dakota D is on the racetrack. (4, 3)
Because of the simulpost I’m not sure which puzzle is officially in play. But I can clarify for mine, I considered the second word of the answer to be “three”. So therein (or thereon 
) lies the overlap.
For the third time my pee is interrupted in the theater.(5-4)
THREE-PEAT (Theater* with PE)
+++++
Surprisingly, Martian desert might provide sources of fruit. (8, 5)
±±±
OR
±±±
Noisy North Dakota D is on the racetrack. (4, 3)
INDY 500 (“N-D” D=500)
+++++
All those years in college and I got nothing to show for it. That’s cold. (1, 7)
TAMARIND TREES
0 DEGREES
Well done getting us back on track Biotop!
On Easter Sunday, we took out the sedan and visited the inlet.(7)
Estuary (Easter Sunday - sedan)
++++
Blathering on about bovines in the city and elsewhere (7,3)
YAKKITY YAK (double definition)
+++++
Zeroes have the suspected keys, not the usually confused agents. (6,4)
Correct answer. By way of explanation, when I made the clue I was using what was, unbeknownst to me at the time, a misspelling of that term as “yackity yak”. Hence the “bovines in the city” part of the clue. My mistake. Please carry on with Prof’s puzzle:
Keyser Soze (anagram zeroes + keys)
++++
Spell out a description of erstwhile simplicity (7)
EXPLAIN (ex-plain = erstwhile simplicity)
Food gives new plenty (7)
Noodles (n + oodles)?
Yup xx
Off NOODLES:
Playing with the eel? I’m sure it has nothing better to do (7,4)
Off NOODLES:
Playing with the eel? I’m sure it has nothing better to do (7,4)
I can anagram LEISURE TIME, but it does not play off of NOODLES.
You Jedi mind read through my spelling error! That is indeed the solution. Please take it away.
LEISURE TIME (anagram of “eelimsureit”)
+++++
I fear filming the Lost actress. (7, 8)
I am just going to assume no help is needed here…