Old member overwhelmed by drink, for instance (7)
I believe the answer is:
example
'instance' is the definition.
('example' can be a synonym of 'instance')
'old member overwhelmed by drink' is the wordplay.
'old' becomes 'ex'.
'member' becomes 'mp'.
'overwhelmed by' indicates putting letters inside (I've seen this in other clues).
'drink' becomes 'ale' (ale is a kind of drink).
'mp' inserted into 'ale' is 'ample'.
'ex'+'ample'='EXAMPLE'
'for' acts as a link.
(Other definitions for example that I've seen before include "lesson" , "Illustration or model" , "Characteristic item" , "Precedent" , "Paradigm or model" .)