To finish breakfast, a little drink (3)
I believe the answer is:
tot
'a little drink' is the definition.
(tot can mean a small drink of alcohol)
'to finish breakfast' is the wordplay.
'finish' indicates one should take the final letters.
The last letter of 'breakfast' is 't'.
'to'+'t'='TOT'
(Other definitions for tot that I've seen before include "Sum for the little one" , "Drop" , "Small drink - young child" , "Nip" , "Aggregate for infant" .)