He should know one port from another (4,6)
I believe the answer is:
wine taster
'he should know one port from another' is the definition.
I know nothing about this answer so I can't tell whether this works.
'he should know one port from another' is the wordplay.
I cannot really see how this works, but
'he' could be 'win' and 'win' is found within the answer.
'one' could be 'a' (a thing is one thing) and 'a' is found within the answer.
'from' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'another' could be 'r' (I've seen this in other clues) and 'r' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for wine taster that I've seen before include "judge turning to drink" , "Person presented bouquets, perhaps" , "Drinks sampler" , "Person with refined palate" .)