Not much time for boxers' assistants (7)
I believe the answer is:
seconds
This clue might be a double definition.
'not much time' is the first definition.
(a second is a short amount of time)
'boxers' assistants' is the second definition.
'seconds' can be an answer for 'assistants' (second is a kind of assistant). I'm not certain of the 'boxers'' bit.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for seconds that I've seen before include "They should be present at a duel" , "Supports motion" , "Endorses proposal" , "Imperfect goods at reduced prices" , "in a minute!" .)