Theme: BYWORDS — Ok. Obviously something with BY. And we have circles. Notice that the sets of circles are lined up next to each other. Might these two things be related? Solve one pair of down clues with circles and all will become clear! (Side effect of the way this theme works: It’s not about the long clues/answers as such, just the circled letters).
Theme (using 47- and 42- down). Half of how Noah loaded the ark. (And the things that may be written in it aren’t likely to be changed very easily!)
Paisley refusals: Bet you thought of 60’s clothes, right? Nah. Paisley is also a place.
F = ma formulator: Amazing that this same man invented a fig-filled cookie!
Revolutionary 1960s Chinese youth: 2 words
Attach a handle to: Not the kind of handle you can hold onto, at least not physically.
Quibblers split them: This one could have a question mark (pun indicator) after it.
One running: Think election
Derby features: Don’t think races
Go out: Think tide