Drunk, returning no port (3,2)

'port' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'drunk returning no' is the wordplay.
I cannot quite see how this works, but
'drunk' could be 'sot' (both can mean someone who drinks too much) and 'sot' is present in the answer.
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is present in the answer.
A single letter 'n' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?