Pattern shown by former politician getting into drink (7)
I believe the answer is:
example
'pattern' is the definition.
(thesaurus)
'former politician getting into drink' is the wordplay.
'former' becomes 'ex'.
'politician' becomes 'mp'.
'getting into' means one lot of letters goes inside another.
'drink' becomes 'ale' (ale is a kind of drink).
'mp' put into 'ale' is 'ample'.
'ex'+'ample'='EXAMPLE'
'shown by' acts as a link.
(Other definitions for example that I've seen before include "Something to be imitated" , "Model - instance" , "Illustration or paradigm" , "lesson" , "Someone to emulate" .)