Pudding with a drop of rum in elaborate feast (6)
I believe the answer is:
afters
'pudding' is the definition.
(both can mean dessert)
'drop of rum in elaborate feast' is the wordplay.
'drop of' suggests taking the first letters (the smallest possible amount of the word).
'in' is an insertion indicator.
'elaborate' is an anagram indicator (an elaborate version of the letters).
The initial letter of 'rum' is 'r'.
'feast' with letters rearranged gives 'aftes'.
'r' put inside 'aftes' is 'AFTERS'.
'with a' acts as a link.
(Other definitions for afters that I've seen before include "Dessert (colloq.)" , "Dessert, sweet" , "Strafe with desserts" , "Informal desserts, puddings" , "food for pudding" .)