Port fine to be knocked back with half of beer (4)
I believe the answer is:
kobe
'port' is the definition.
(Japanese port)
'fine to be knocked back with half of beer' is the wordplay.
'fine' becomes 'OK' (synonyms).
'to be knocked back' says the letters should be written backwards.
'with' means one lot of letters go next to another.
'half of' suggests halving the letters.
'ok' written backwards gives 'ko'.
'beer' with half the letters taken is 'be'.
'ko'+'be'='KOBE'
(Other definitions for kobe that I've seen before include "Japanese port, hit by an earthquake in 1995" , "Japanese 1995 earthquake site; be OK (anag.)" , "City in Japan" , "Eastern port" .)