Labour's leader got wise (7)
I believe the answer is:
learned
'wise' is the definition.
(I've seen this before)
'labour's leader got' is the wordplay.
'labour's leader' becomes 'l'.
'got' becomes 'earned' (earning is a kind of getting).
'l'+'earned'='LEARNED'
(Other definitions for learned that I've seen before include "widely read" , "Got to know" , "Erudite, knowledgeable" , "Discovered, ascertained" , "Highly educated" .)