To a beginner, dry wine is very rough! (6)
I believe the answer is:
brutal
'rough' is the definition.
(thesaurus)
'to a beginner' is the wordplay.
'to' becomes 'brut' (I can't explain this - if you can you should give a lot more credence to this answer).
'beginner' becomes 'l'.
'brut'+'a'+'l'='BRUTAL'
'dry wine is very' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for brutal that I've seen before include "Very cruel, merciless" , "Cruel, animal-like" , "Very cruel and beastly" , "Rough and cruel" , "Senselessly cruel" .)