Clean ship's prow with sailor (4)
I believe the answer is:
swab
'clean' is the definition.
(swabbing is a kind of cleaning)
'ship's prow with sailor' is the wordplay.
'prow' indicates taking the first letters.
'with' becomes 'w' (short for with).
'sailor' becomes 'ab' (abbreviation for able seaman).
The initial letter of 'ships' is 's'.
's'+'w'+'ab'='SWAB'
(Other definitions for swab that I've seen before include "Surgical cleaner" , "Cleaning implement" , "Clean (a wound)" , "Absorbent pad for cleansing or drying" , "Cloth for cleaning wounds" .)