Carry support for a whale (8)
I believe the answer is:
humpback
'whale' is the definition.
(I know that humpback is a type of baleen whale)
'carry support' is the wordplay.
'carry' becomes 'hump' (I've seen this before).
'support' becomes 'back' (to back is to support or endorse).
'hump'+'back'='HUMPBACK'
'for a' is the link.
(Other definitions for humpback that I've seen before include "Type of whale" , "Handicap" , "Whale - kind of bridge" , "Variety of whale or bridge" .)