Lean page to allow endless drink (6)
I believe the answer is:
tipple
'drink' is the definition.
(tipple is a kind of drink)
'lean page to allow endless' is the wordplay.
'lean' becomes 'tip' (synonyms).
'page' becomes 'p'.
'to allow' becomes 'let' ('let' can be a synonym of 'allow').
'endless' means to remove the last letter.
'let' with its final letter removed is 'le'.
'tip'+'p'+'le'='TIPPLE'
(Other definitions for tipple that I've seen before include "Habitually drink in small quantities" , "Paint < pot" , "Snifter" , "Drink alcohol habitually" , "(Regular) alcoholic drink" .)