One politician wandering, making progress (9)
I believe the answer is:
improving
'making progress' is the definition.
'one politician wandering' is the wordplay.
'one' becomes 'i' (Roman numeral).
'politician' becomes 'MP' (Member of Parliament).
'wandering' becomes 'roving' (synonyms).
'i'+'mp'+'roving'='IMPROVING'
(Other definitions for improving that I've seen before include "Making better" , "Getting better" , "Recovering" .)