Criminal not many go to stop, perhaps (7)
I believe the answer is:
antonym
'go to stop perhaps' is the definition.
('go' is the opposite or antonym of 'stop')
'criminal not many' is the wordplay.
'criminal' indicates an anagram.
'not'+'many'='notmany'
'notmany' anagrammed gives 'ANTONYM'.
(Other definitions for antonym that I've seen before include ""Loud" as opposed to "quiet", for example" , "something completely different" , "One's import is contrary" , "Word that means the opposite of another" , "opposing description" .)