Cocky, for a time (4)
I believe the answer is:
pert
'cocky' is the definition.
(thesaurus)
'a time' is the wordplay.
'a' becomes 'per'.
'time' becomes 't'.
'per'+'t'='PERT'
'for' is the link.
(Other definitions for pert that I've seen before include "Saucy and impudent" , "Persian expert" , "Saucy and chipper" , "Forward - saucy" , "It's fresh" .)