Fully developed blend of tea and rum (6)
I believe the answer is:
mature
'fully developed' is the definition.
(I've seen this before)
'blend of tea and rum' is the wordplay.
'blend of' is an anagram indicator (I've seen this in other clues).
'and' is a charade indicator (letters next to each other) (I've seen this in other clues).
'tea' put after 'rum' is 'rumtea'.
'rumtea' with letters rearranged gives 'MATURE'.
(Other definitions for mature that I've seen before include "Fully developed physically" , "Old film star" , "Full-grown - ripe" , "Age" , "Ripe or fully grown" .)