Irritable Charlie, a drop-out (6)
I believe the answer is:
chippy
'irritable' is the definition.
(chippy can mean sensitive or irritable)
'charlie a drop-out' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'a drop-out' becomes 'hippy' (drop-out can mean a hippy or bohemian).
'c'+'hippy'='CHIPPY'
(Other definitions for chippy that I've seen before include "Carpenter - fast food outlet" , "Carpenter - for fried food!" , "Carpenter - touchy" , "Takeaway (sl.)" , "Shop selling fried potatoes - carpenter" .)