Go off in step, anyhow, and march (7)
I believe the answer is:
protest
'march' is the definition.
(thesaurus)
'go off in step anyhow' is the wordplay.
'go off' becomes 'rot' (as in food going off).
'in' means one lot of letters goes inside another.
'anyhow' is an anagram indicator.
'step' is an anagram of 'pest'.
'rot' inserted within 'pest' is 'PROTEST'.
'and' is the link.
(Other definitions for protest that I've seen before include "Take exception" , "Object loudly" , "Statement or action showing disapproval" , "Demurral" , "Express opposition" .)