A relation of a southern politician (5)
I believe the answer is:
story
'a relation' is the definition.
(story is a kind of relation)
'a southern politician' is the wordplay.
'a southern' becomes 's' (abbreviation).
'politician' becomes 'tory' (term for a Conservative Party politician).
's'+'tory'='STORY'
'of' is the link.
(Other definitions for story that I've seen before include "Tale - lie" , "Narration" , "Account, tale" , "Narrative or account" , "Anecdote" .)