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 in other clues).
'about it' is an insertion indicator (some letters go around or about others).
'rot' going inside 'pest' is 'PROTEST'.
'will' acts as a link.
(Other definitions for protest that I've seen before include "Showing support" , "Public demonstration" , "Objection from potters" , "Complaint" , "Statement or action showing disapproval" .)