Smears fingerprints (4)
I believe the answer is:
dabs
This clue is a double definition.
'smears' is the first definition.
'fingerprints' is the second definition.
(I've seen this before)
(Other definitions for dabs that I've seen before include "prints" , "Informal adepts or kind of flat-fish" , "'Pats at, with a cloth, say (4)'" , "Fish; fingerprints" , "they give evidence to police" .)