Lawyer for king tries cocktail in watering hole (9)
I believe the answer is:
barrister
'lawyer' is the definition.
(barrister is a kind of lawyer)
'king tries cocktail in watering hole' is the wordplay.
'king' becomes 'r' (r is abbreviation for rex).
'cocktail' indicates an anagram.
'in' means one lot of letters goes inside another.
'watering hole' becomes 'bar' (I've seen this before).
'r'+'tries'='rtries'
'rtries' anagrammed gives 'rriste'.
'rriste' going inside 'bar' is 'BARRISTER'.
'for' acts as a link.
(Other definitions for barrister that I've seen before include "Court lawyer" , "Legal counsel" , "A bewigged legal eagle" , "Rarest rib for the eminent lawyer" , "Legal representative" .)