Beef will go off; that's the nuisance about it (7)
I believe the answer is:
protest
'beef' is the definition.
(I've seen this in another clue)
'go off that's the nuisance about it' is the wordplay.
'go off' becomes 'rot' (as in food going off).
'that's the nuisance' becomes 'pest' (I've seen this before).
'about it' means one lot of letters goes inside another (some letters go around or about others).
'rot' placed inside 'pest' is 'PROTEST'.
'will' is the link.
(Other definitions for protest that I've seen before include "Showing support" , "Public demonstration" , "Objection from potters" , "Complaint" , "Statement or action showing disapproval" .)