Close to harbour, sailor in coat bows (5)
I believe the answer is:
rosin
'coat bows' is the definition.
(rosin can mean to coat a violin bow in rosin)
'close to harbour sailor in' is the wordplay.
'close to' says to take the final letters (the 'close' to the word).
'sailor' becomes 'os' (ordinary seaman).
The last letter of 'harbour' is 'r'.
'r'+'os'+'in'='ROSIN'
(Other definitions for rosin that I've seen before include "It's put on bow" , "Violin bow treatment" , "Rub it along the violin bow" , "Fiddler's resin" , "Wax for violin bow etc." .)