The provision, for money, of a small drink (4)
I believe the answer is:
sale
'the provision for money' is the definition.
I can't tell whether this definition defines the answer.
'a small drink' is the wordplay.
'a small' becomes 's' (abbreviation - e.g. clothes size).
'drink' becomes 'ale' (type of beer).
's'+'ale'='SALE'
'of' is the link.
Can you help me to learn more?
(Other definitions for sale that I've seen before include "Offer period" , "From which one may get bargains" , "Bargain-price event" , "Transaction" , "Period of reduced prices" .)