Guinness, perhaps, or a beer that's cold (4)
I believe the answer is:
alec
'guinness perhaps' is the definition.
(actor Alec Guinness)
'beer that's cold' is the wordplay.
'beer' becomes 'ale' (type of beer).
'that's cold' becomes 'C' (eg on taps).
'ale'+'c'='ALEC'
'or a' is the link.
(Other definitions for alec that I've seen before include "A smart . . . . is a know-all in lace" , "Guinness (a smart lad?)" , "Smart man?" , "Smart ..., he thinks he knows everything" , "Boy's name (a smart one?)" .)