See, beer can be so rough (6)
I believe the answer is:
choppy
'rough' is the definition.
(I've seen this before)
'see beer' is the wordplay.
I cannot quite understand how this works, but
'see' could be 'c' (the word for the letter, according to Chambers) and 'c' is located in the answer.
The remaining letters 'hoppy' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'can be so' is the link.
Can you help me to learn more?
(Other definitions for choppy that I've seen before include "Jerky" , "(Of the sea) a bit rough" , "Somewhat rough (sea)" , "Moderately rough (sea)" , "Describes a rough sea with small waves" .)