Short time (6)
I believe the answer is:
second
'short time' is the definition.
(second is a kind of short time)
This is the entire clue.
(Other definitions for second that I've seen before include "A boxer's corner assistant - not the first" , "Time for a supporter" , "Position of runner-up" , "Attendant in a duel or boxing match" , "Silver medal position" .)