Catch and knock out with a right! (4)
I believe the answer is:
trap
'catch' is the definition.
(trapping is a kind of catching)
'knock out with a right' is the wordplay.
'knock out' becomes 'tap' (synonyms. I am not sure about the 'out' bit.).
'with' means one lot of letters goes inside another.
'a right' becomes 'r' (common abbreviation).
'tap' going around 'r' is 'TRAP'.
'and' is the link.
Can you help me to learn more?
(Other definitions for trap that I've seen before include "Golfing hazard" , "Driver's obstacle" , "Cakehole (slang)" , "get in net" , "fault" .)