Celebration for political group (5)
I believe the answer is:
party
This clue is a double definition.
'celebration' is the first definition.
(I've seen this before)
'political group' is the second definition.
(a political party)
'for' acts as a link.
(Other definitions for party that I've seen before include "Shooting weapon" , "Group gathered together for pleasure" , "Political organisation" , "Political group - celebration" , "Social occasion - political group" .)