Party caught a politician (4)
I believe the answer is:
camp
'party' is the definition.
(both can mean a group of people)
'caught a politician' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'politician' becomes 'MP' (Member of Parliament).
'c'+'a'+'mp'='CAMP'
(Other definitions for camp that I've seen before include "Tent site" , "Temporary military site" , "A tent, or effeminate in style" , "holiday venue" , "Extensive outdoor facility" .)