Sailors may take a turn round them (5)
I believe the answer is:
bitts
'round them' is the definition.
I can't judge whether this defines the answer.
'sailors may take a turn' is the wordplay.
'sailors may' becomes 'bits' (I can't justify this - if you can you should believe this answer much more).
'take' indicates putting letters inside.
'a turn' becomes 't' (abbreviation in Oxford Dictionary of Abbreviations).
'bits' placed around 't' is 'BITTS'.
Can you help me to learn more?
(Other definitions for bitts that I've seen before include "Posts for securing ship's cables" , "Posts for securing cables etc" .)