Taxi taken by a large political clique (5)
I believe the answer is:
cabal
'political clique' is the definition.
(I've seen this before)
'taxi taken by a large' is the wordplay.
'taxi' becomes 'cab' (synonyms).
'taken by' is a charade indicator (letters next to each other).
'large' becomes 'L' (eg in clothes sizes).
'cab'+'a'+'l'='CABAL'
(Other definitions for cabal that I've seen before include "Secret political group" , "Clique of plotters" , "Group in plot" , "Plotting group" , "Intrigue, clique" .)