Heartless Del Boy perhaps on the rise, making a comeback (6)
I believe the answer is:
retort
'a comeback' is the definition.
(I know that comeback can be written as retort)
'heartless del boy perhaps on the rise' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'del boy perhaps' becomes 'trotter' (as in Del Boy Trotter from Only Fools and Horses).
'on the rise' says the letters should be written in reverse (in a down clue, letters go up).
'trotter' with its centre removed is 'troter'.
'troter' reversed gives 'RETORT'.
'making' is the link.
(Other definitions for retort that I've seen before include "Answer back" , "Glass vessel used in distilling liquids" , "Still" , "A quick, sharp reply" , "Lab. vessel; quip" .)