Sailor bound to drink nip of tawny port (6)

I believe the answer is:
ostend
'port' is the definition.
(I've seen this before)
'sailor bound to drink nip of tawny' is the wordplay.
I cannot really understand how this works, but
'sailor' could be 'os' (ordinary seaman) and 'os' is located in the answer.
'bound' could be 'end' (end is a kind of bound) and 'end' is found in the answer.
A single letter 't' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ostend that I've seen before include "cross-channel port" , "Channel port" , "Belgian port and resort" , "Port - doesn't (anag)" , "Port in Belgium" .)
