Arresting outlaw to criticise a head honcho (3,6)
I believe the answer is:
top banana
'head honcho' is the definition.
(I've seen this in another clue)
'arresting outlaw to criticise a' is the wordplay.
'arresting' means one lot of letters goes inside another.
'outlaw' becomes 'ban' (banning is a kind of outlawing).
'criticise' becomes 'pan' (informal term meaning to criticise heavily).
'to'+'pan'='topan'
'ban' placed into 'topan' is 'topbanan'.
'topbanan'+'a'='TOP BANANA'
(Other definitions for top banana that I've seen before include "pick of the bunch?" , "figurehead?" , "first on hand?" , "head" , "Star entertainer" .)