Port does as rum (6)
I believe the answer is:
odessa
'port' is the definition.
(I've seen this before)
'does as rum' is the wordplay.
'rum' is an anagram indicator (rum can mean strange or unusual).
'does'+'as'='doesas'
'doesas' anagrammed gives 'ODESSA'.
(Other definitions for odessa that I've seen before include "Port city on the Black Sea" , "Black Sea location" , "Do seas come into Ukrainian city?" , "Ukrainian location" , "Ukrainian Black Sea port" .)