Clean with a mop (4)
I believe the answer is:
swab
'clean with a mop' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for swab that I've seen before include "Clean (a wound)" , "Piece of fabric for medical use" , "Surgical cleaner" , "Pad used in surgery" , "Hospital cleaner" .)