Beer: first choice is Guinness (4)
I believe the answer is:
alec
'is guinness' is the definition.
(actor Alec Guinness)
'beer first choice' is the wordplay.
'beer' becomes 'ale' (type of beer).
'first choice' becomes 'c' (1st letter of 'choice').
'ale'+'c'='ALEC'
(Other definitions for alec that I've seen before include "Actor Guinness is smart" , "Sir - Douglas-Home, former PM" , "Guinness (a smart lad?)" , "Smart ..., he thinks he knows everything" , "Smart chap" .)