Crazed fellow in charge (5)
I believe the answer is:
manic
'crazed' is the definition.
(I've seen this in another clue)
'fellow in charge' is the wordplay.
'fellow' becomes 'man' (fellow can mean a man).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'man'+'ic'='MANIC'
(Other definitions for manic that I've seen before include "Crazily excited" , "Berserk" , "Obsessive" , "on one!" , "Ludicrously busy" .)