Small amount of time used with advantage (3)
I believe the answer is:
tad
'small amount' is the definition.
('a tad' is a small amount)
'time used with advantage' is the wordplay.
'time' becomes 't' (abbreviation).
'used with' is a charade indicator (letters next to each other).
'advantage' becomes 'ad' (I've seen this in other clues).
't'+'ad'='TAD'
'of' is the link.
(Other definitions for tad that I've seen before include "Small amount or degree" , "Slight amount" , "Modest amount" , "Little bit" , "A small amount (colloq.)" .)