A drained pint is spot-on (3)
I believe the answer is:
apt
'spot-on' is the definition.
(I've seen this in another clue)
'a drained pint' is the wordplay.
'drained' says to hollow out the word (remove centre letters).
'pint' with its middle taken out is 'pt'.
'a'+'pt'='APT'
'is' acts as a link.
(Other definitions for apt that I've seen before include "clever" , "apartment in Queens, say" , "Having a tendency" , "Tap (anag.)" , "suitable for the circumstances" .)