Dubious sort with alcoholic drink on platform (7)
I believe the answer is:
rostrum
'platform' is the definition.
(rostrum is a kind of platform)
'dubious sort with alcoholic drink' is the wordplay.
'dubious' indicates an anagram.
'with' says to put letters next to each other.
'alcoholic drink' becomes 'rum' (I've seen this before**).
'sort' anagrammed gives 'rost'.
'rost'+'rum'='ROSTRUM'
'on' acts as a link.
(Other definitions for rostrum that I've seen before include "At which one may conduct" , "Platform for public speaking" , "Rum rots (anag)" , "Platform for public speakers" , "stage" .)