Way to encourage a swimmer (8)
I believe the answer is:
sturgeon
'a swimmer' is the definition.
(sturgeon is a kind of fish)
'way to encourage' is the wordplay.
'way' becomes 'st'.
'to encourage' becomes 'urgeon' (urging on is a kind of encouraging).
'st'+'urgeon'='STURGEON'
(Other definitions for sturgeon that I've seen before include "caviar suppliers" , "Fish that yields caviare" , "Egg producer" , "Fish yielding caviar and isinglass" , "Source of caviare and isinglass" .)