Ant panicked a politician with the habit of swimming (8)
I believe the answer is:
natatory
'with the habit of swimming' is the definition.
(natatory means relating to swimming)
'ant panicked a politician' is the wordplay.
'panicked' indicates anagramming the letters.
'politician' becomes 'tory' (I've seen this before).
'ant' anagrammed gives 'nat'.
'nat'+'a'+'tory'='NATATORY'
(Other definitions for natatory that I've seen before include "Of swimming" , "habit of a floating voter?!" .)