Mellow rum and tea concoction (6)
I believe the answer is:
mature
'mellow' is the definition.
(similar in meaning)
'rum and tea concoction' is the wordplay.
'and' is a charade indicator (letters next to each other).
'concoction' is an anagram indicator.
'rum' put after 'tea' is 'tearum'.
'tearum' with letters rearranged gives 'MATURE'.
(Other definitions for mature that I've seen before include "Ripe or fully grown" , "Full-grown - ripe" , "due to be paid" , "Fully-developed" , "Old film star" .)