Answer included in new collection of corniest answers (9)
I believe the answer is:
reactions
'answers' is the definition.
'answer included in new collection of corniest' is the wordplay.
'answer' becomes 'a' (abbreviation eg in Q and A).
'included in' means one lot of letters goes inside another.
'new collection of' indicates anagramming the letters.
'corniest' with letters rearranged gives 'rections'.
'a' going into 'rections' is 'REACTIONS'.
(Other definitions for reactions that I've seen before include "Responses, chemical perhaps" , "Newton's law of motion says all actions have them" , "What you may get with chemicals" , "Takes" , "Mental or physical responses" .)