Clue: After missing Trigger's entrance once perhaps Del Boy recalled witty response (6)
Answer: RETORT
Explanation: Definition: response

**<=(TROT**(t)**ER)** ("perhaps Del Boy", *recalled*, *missing* T(rigger) [*'s entrance*] *once*)
 
*Del Boy Trotter and Trigger were both characters in the sitcom *Only Fools and Horses*.