Fair for one to charge crazy fool? (7)
I believe the answer is:
mislead
'fool?' is the definition.
(thesaurus)
'fair for one to charge crazy' is the wordplay.
'fair for one' becomes 'isle' (Fair Isle is a Scottish island).
'to charge' is an insertion indicator (charge can mean to fill).
'crazy' becomes 'mad' ('mad' can be a synonym of 'crazy').
'isle' going within 'mad' is 'MISLEAD'.
(Other definitions for mislead that I've seen before include "Take someone in the wrong direction" , "Give a wrong impression to (someone)" , "Cause someone to believe something is not true" , "Hoodwink" , "Deceive" .)