The way to encourage fish (8)
I believe the answer is:
sturgeon
'fish' is the definition.
(sturgeon is a kind of fish)
'the way to encourage' is the wordplay.
'the 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 "Fish that yields caviare" , "Shark-like fish" , "Fish yielding caviar and isinglass" , "Egg producer" , "Fish producing caviar" .)