After missing Trigger's entrance once perhaps Del Boy recalled witty response (6)
I believe the answer is:
retort
'response' is the definition.
(I know that retort is a type of response)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for retort that I've seen before include "swift return" , "Make quick or angry reply" , "Rotter (anag.)" , "Quick rejoinder" , "Snappy reply" .)