Saucy, for a time (4)
I believe the answer is:
pert
'saucy' is the definition.
(synonyms)
'a time' is the wordplay.
'a' becomes 'per' (eg 'one a day' means 'one per day').
'time' becomes 't' (abbreviation).
'per'+'t'='PERT'
'for' acts as a link.
(Other definitions for pert that I've seen before include "Forward - saucy" , "Saucy, maybe brash" , "Jaunty" , "Saucy and chipper" , "Saucy, lively" .)