Young swimmer needing a little support (7)
I believe the answer is:
tadpole
'young swimmer' is the definition.
(young frog)
'a little support' is the wordplay.
'a little' becomes 'tad' (both can mean a small amount).
'support' becomes 'pole' (poling is a kind of supporting).
'tad'+'pole'='TADPOLE'
'needing' is the link.
(Other definitions for tadpole that I've seen before include "little swimmer" , "Young Kermit" , "immature sea squirt" , "youngster" , "To plead for tiny frog" .)