Wine and port a judge knocked back (5)
I believe the answer is:
rioja
'wine' is the definition.
(Rioja is an example)
'port a judge knocked back' is the wordplay.
'port' becomes 'rio' (I've seen this before).
'judge' becomes 'j'.
'knocked back' shows that the letters should be reversed in order.
'a'+'j'='aj'
'aj' in reverse letter order is 'ja'.
'rio'+'ja'='RIOJA'
'and' acts as a link.
(Other definitions for rioja that I've seen before include "wine region" , "Spanish red wine" , "Spanish drink" , "North Spanish wine" , "Dry red wine from Spain" .)