Strike nail after a time (6)
I believe the answer is:
attack
'strike' is the definition.
(I've seen this before)
'nail after a time' is the wordplay.
'nail' becomes 'tack' (tack is a kind of nail).
'after' is a charade indicator (letters next to each other).
'time' becomes 't'.
'a'+'t'='at'
'tack' after 'at' is 'ATTACK'.
(Other definitions for attack that I've seen before include "Publicly criticise" , "Assault, offensive" , "Show aggression" , "Raid" , "An assault or onslaught" .)