Unconventional sort found on odd platform (7)
I believe the answer is:
rostrum
'platform' is the definition.
(rostrum is a kind of platform)
'unconventional sort found on odd' is the wordplay.
'unconventional' indicates an anagram.
'found on' is a charade indicator (letters next to each other).
'odd' becomes 'rum' (I've seen this before).
'sort' anagrammed gives 'rost'.
'rost'+'rum'='ROSTRUM'
(Other definitions for rostrum that I've seen before include "Conductor's dais" , "stage" , "At which one may conduct" , "place for speaker" , "Raised platform" .)