Agree with politician, a despicable sort (6)
I believe the answer is:
concur
'agree with' is the definition.
(I've seen this before)
'politician a despicable sort' is the wordplay.
'politician' becomes 'con'.
'a despicable sort' becomes 'cur' (I've seen this in another clue).
'con'+'cur'='CONCUR'
(Other definitions for concur that I've seen before include "'Agree, coincide (6)'" , "Give assent" , "Agree, assent" , "See eye to eye" , "run together" .)