After drink, sat and thought (8)
I believe the answer is:
supposed
'thought' is the definition.
('suppose' can be a synonym of 'think')
'after drink sat' is the wordplay.
'after' is a charade indicator (letters next to each other).
'drink' becomes 'sup' (to sup is to drink).
'sat' becomes 'posed' ('pose' can be a synonym of 'sit').
'sup' next to 'posed' is 'SUPPOSED'.
'and' acts as a link.
(Other definitions for supposed that I've seen before include "So-called" , "Putative" , "Assumed without proof" , "Assumed - hypothetical" , "Reckoned, took to be the case" .)