Box of spares? (4)
I believe the answer is:
spar
This clue might be a double definition.
'box' is the first definition.
(sparring is a kind of boxing)
'of spares?' is the second definition.
The definition suggests a singular noun which matches the answer.
Can you help me to learn more?
(Other definitions for spar that I've seen before include "Practise boxing with a pole?" , "Stout pole to support rigging" , "Box - girder" , "Pole used in rigging - fight" , "dispute" .)