Man perhaps stops crazy fool (7)
I believe the answer is:
mislead
'fool' is the definition.
(thesaurus)
'man perhaps stops crazy' is the wordplay.
'man perhaps' becomes 'isle' (I've seen this before).
'stops' means one lot of letters goes inside another.
'crazy' becomes 'mad' ('mad' can be a synonym of 'crazy').
'isle' inserted into 'mad' is 'MISLEAD'.
(Other definitions for mislead that I've seen before include "Hoodwink" , "Fool" , "Cause someone to believe something is not true" , "Give a wrong impression to (someone)" , "Cause someone to have a false belief" .)