Political activist is able very shortly to take in fool (9)
I believe the answer is:
canvasser
'political activist' is the definition.
(someone canvassing for votes)
'able very shortly to take in fool' is the wordplay.
'able' becomes 'can'.
'shortly' means to remove the last letter.
'to take in' indicates putting letters inside.
'fool' becomes 'ass' (both can mean a stupid person).
'very' with its final letter taken away is 'ver'.
'ver' going around 'ass' is 'vasser'.
'can'+'vasser'='CANVASSER'
'is' is the link.
(Other definitions for canvasser that I've seen before include "Seeker of opinions" , "Electioneer" , "Political assistant" , "solicitor" , "One soliciting votes" .)