Light pat (3)
I believe the answer is:
dab
'light pat' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dab that I've seen before include "Fish; small amount" , "Touch gently - fingerprint" , "Bad sort of small fish" , "Apply light touches of colour to the fish" , "Fingerprint - fish" .)