Fish; fingerprint (3)
I believe the answer is:
dab
This clue is a double definition.
'fish' is the first definition.
(dab is a type of fish)
'fingerprint' is the second definition.
(I've seen this before)
(Other definitions for dab that I've seen before include "Apply small amounts (usually a liquid) to a surface" , "Apply light touches of colour to the fish" , "Lightly press" , "Flatfish; fingerprint" , "Bad kind of fish" .)