Crossword Genius

Motivation to share drink (9)

Ross

I believe the answer is:

rationale

'motivation' is the definition.
(I've seen this before)

'share drink' is the wordplay.
'share' becomes 'ration' (ration is a kind of share).
'drink' becomes 'ale' (I've seen this before).
'ration'+'ale'='RATIONALE'

'to' is the link.

(Other definitions for rationale that I've seen before include "Good reason" , "Why regulate" , "This might account for" , "grounds?" , "Reasoned exposition" .)

I've seen this clue in The Guardian.
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