Carrying mature wine on top (7)
I believe the answer is:
portage
'carrying' is the definition.
(thesaurus)
'mature wine on top' is the wordplay.
'mature' becomes 'age' ('age' can be a synonym of 'mature').
'wine' becomes 'port' (port is a kind of wine**).
'on top' is a charade indicator (letters next to each other) (down clues only).
'age' put after 'port' is 'PORTAGE'.
(Other definitions for portage that I've seen before include "Carriage" , "Transport between waterways" , "Carrying boat overland" , "Cost of carrying or transporting" .)