A small amount of fish (3)
I believe the answer is:
dab
I believe this clue is a double definition.
'a small amount' is the first definition.
(I've seen this before)
'fish' is the second definition.
(dab is a type of fish)
'of' is the link.
(Other definitions for dab that I've seen before include "Touch gently - fingerprint" , "Small North Atlantic flatfish" , "Apply small amounts (usually a liquid) to a surface" , "A small fish - bad one" , "Flounder" .)