Applies to fingerprints (4)
I believe the answer is:
dabs
This clue is a double definition.
'applies' is the first definition.
(dabbing is a kind of applying)
'fingerprints' is the second definition.
(dab can mean a fingerprint)
'to' acts as a link.
(Other definitions for dabs that I've seen before include "finger traces" , "Fingerprints (sl.)" , "Applies light touches" , "Fingerprints (informal)" , "Fish; fingerprints" .)