Think about one drink in eight, say (8)
I believe the answer is:
ruminate
'think' is the definition.
(ruminating is a kind of thinking)
'one drink in eight say' is the wordplay.
'one drink' becomes 'rum' (rum is a kind of drink**).
'say' indicates a 'sounds like' (homophone) clue.
'eight' sounds like 'ate'.
'rum'+'in'+'ate'='RUMINATE'
'about' acts as a link.
(Other definitions for ruminate that I've seen before include "'Reflect deeply, chew the cud (8)'" , "Contemplate" , "Seriously consider" , "deliberate" , "Cogitate" .)