Fight, second, of expected standard (4)
I believe the answer is:
spar
'fight' is the definition.
(sparring is a kind of fighting)
'second of expected standard' is the wordplay.
'second' becomes 's' (common abbreviation).
'of expected standard' becomes 'par'.
's'+'par'='SPAR'
(Other definitions for spar that I've seen before include "Yard" , "Do up (bird for oven)" , "Crystalline mineral" , "Go a few rounds with the ship's pole" , "Practice boxing with wooden beam" .)