A brief way to stimulate fish (8)
I believe the answer is:
sturgeon
'fish' is the definition.
(sturgeon is a kind of fish)
'a brief way to stimulate' is the wordplay.
'a brief way' becomes 'st' (abbreviation for street; 'brief' asks for an abbreviation).
'to stimulate' becomes 'urgeon' (I can't explain this - if you can you should give a lot more credence to this answer).
'st'+'urgeon'='STURGEON'
Can you help me to learn more?
(Other definitions for sturgeon that I've seen before include "Fish yielding caviar and isinglass" , "Egg producer" , "Fish producing caviar" , "Caviar supplier" , "Caviare-producing fish" .)