Cold beer to start? Smart man! (4)
I believe the answer is:
alec
'smart man' is the definition.
(as in the phrase 'smart Alec')
'cold beer to start?' is the wordplay.
'cold' becomes 'C' (eg on taps).
'beer' becomes 'ale' (type of beer).
'to start?' is a charade indicator (letters next to each other).
'c' after 'ale' is 'ALEC'.
(Other definitions for alec that I've seen before include "Smart ..., he thinks he knows everything" , "Sir -- Guinness, actor" , "Guinness (a smart lad?)" , "Boy's name (a smart one?)" , "Smart man?" .)