Odd business gets rare treatment (7)
I believe the answer is:
bizarre
'odd' is the definition.
(I've seen this before)
'business gets rare treatment' is the wordplay.
'business' becomes 'biz' (biz is a kind of business).
'gets' is a charade indicator (letters next to each other).
'treatment' is an anagram indicator.
'rare' anagrammed gives 'arre'.
'biz'+'arre'='BIZARRE'
(Other definitions for bizarre that I've seen before include "Funny" , "Off-the-wall" , "Weird, outlandish" , "Way-out" , "Weird, grotesque" .)