He pours cocktail for brilliant classical musician (7)
I believe the answer is:
orpheus
'classical musician' is the definition.
(I've seen this before)
'he pours cocktail' is the wordplay.
'cocktail' indicates anagramming the letters.
'he'+'pours'='hepours'
'hepours' anagrammed gives 'ORPHEUS'.
'for brilliant' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for orpheus that I've seen before include "Legendary lyre-playing poet" , "Thracian poet" , "Husband to Eurydice" , "Lyre player of myth" , "musician inspiring many" .)