Irritated chap cut short FBI agent (6)
I believe the answer is:
chafed
'irritated' is the definition.
(chafing is a kind of irritating)
'chap cut short fbi agent' is the wordplay.
'cut short' means to remove the last letter.
'fbi agent' becomes 'fed' (I've seen this in another clue).
'chap' with its last letter taken off is 'cha'.
'cha'+'fed'='CHAFED'
(Other definitions for chafed that I've seen before include "Became sore from rubbing" , "Made sore from rubbing" , "Rubbed" , "Irritated by rubbing" , "Abraded by rubbing" .)