Funny male in charge undermining firm (5)
I believe the answer is:
comic
'funny' is the definition.
(comic can mean funny or humorous)
'male in charge undermining firm' is the wordplay.
'male' becomes 'm' (common abbreviation).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'undermining' is a charade indicator (letters next to each other).
'firm' becomes 'co' (a firm is a company).
'm'+'ic'='mic'
'mic' put after 'co' is 'COMIC'.
(Other definitions for comic that I've seen before include "Garden perhaps" , "Droll - comedian" , "Priceless" , "Professional joke-teller" , "Amusing, laughable" .)