Used for boxing and often hit during fights (5)
I believe the answer is:
chest
'used for' is the definition.
The definition suggests a singular noun which matches the answer.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for chest that I've seen before include "Part of body; storage box" , "Bra on it" , "It's enclosed by the ribs" , "Large, sturdy box with a lid" , "Large box; thorax" .)