German's OK after port wine (5)
I believe the answer is:
'wine' is the definition.
(Rioja is an example)
'german's ok after port' is the wordplay.
'german's ok' becomes 'ja' (I can't justify this - if you can you should believe this answer much more).
'after' means one lot of letters go next to another.
'port' becomes 'Rio' (Rio de Janeiro is a port).
'ja' after 'rio' is 'RIOJA'.
Can you help me to learn more?
(Other definitions for rioja that I've seen before include "Open space (ancient Greek)" , "Spanish drink" , "Wine from northern Spain" , "wine region" , "Spanish table wine" .)