Oppose repair - he has a short fuse (10)
I believe the answer is:
crosspatch
'he has a short fuse' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'oppose repair' is the wordplay.
'oppose' becomes 'cross' (I've seen this before).
'repair' becomes 'patch' (patching is a kind of repairing).
'cross'+'patch'='CROSSPATCH'
Can you help me to learn more?
(Other definitions for crosspatch that I've seen before include "Grumpy type" , "Grumpy person" , "Churl" , "Ill-tempered person" , "Curmudgeon" .)