Nautical mop (4)
I believe the answer is:
swab
'nautical mop' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for swab that I've seen before include "Small pad for surgical use" , "Surgical cleaner" , "Piece of fabric for medical use" , "Absorbent surgical pad" , "Cleaning implement" .)