Fellow in charge captures a crazy person (6)
I believe the answer is:
maniac
'crazy person' is the definition.
(I've seen this before)
'fellow in charge captures a' is the wordplay.
'fellow' becomes 'man' (fellow can mean a man).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'captures' is an insertion indicator.
'ic' going around 'a' is 'iac'.
'man'+'iac'='MANIAC'
(Other definitions for maniac that I've seen before include "Obsessive enthusiast" , "Very reckless person" , "Wild, perhaps violent, type" , "Can aim (anag.)" , "Insane person" .)