Impudent or cheeky (4)
I believe the answer is:
pert
I believe this clue is a double definition.
'impudent' is the first definition.
(I've seen this before)
'cheeky' is the second definition.
(pert can mean cheeky or insolent)
(Other definitions for pert that I've seen before include "Slightly insolent" , "Impudent, cheeky" , "Persian expert" , "Saucy, maybe brash" , "Irreverent or saucy" .)