Disappointment of group needing support (7)
I believe the answer is:
setback
'disappointment' is the definition.
(I've seen this before)
'group needing support' is the wordplay.
'group' becomes 'set' (both can mean a collection).
'needing' is a charade indicator (letters next to each other).
'support' becomes 'back' (to back is to support or endorse).
'set'+'back'='SETBACK'
'of' is the link.
(Other definitions for setback that I've seen before include "disappointment" , "Snag" , "Reversal of fortune" , "Problem" , "Hitch" .)