Sailor a short distance nearer the stern (5)
I believe the answer is:
abaft
'nearer the stern' is the definition.
(I've seen this before)
'sailor a short distance' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'a' becomes 'an'.
'short' means to remove the last letter.
'distance' becomes 'ft'.
'ab'+'an'='aban'
'aban' with its last letter removed is 'aba'.
'aba'+'ft'='ABAFT'
(Other definitions for abaft that I've seen before include "nearer the stern" , "Astern, at sea" , "(Nautically) behind" , "To the rear" , "Towards the stern of a boat" .)