Power of politician installed in fancy suite (7)
I believe the answer is:
impetus
'power' is the definition.
(thesaurus)
'politician installed in fancy suite' is the wordplay.
'politician' becomes 'mp'.
'installed in' is an insertion indicator.
'fancy' indicates anagramming the letters.
'suite' with letters rearranged gives 'ietus'.
'mp' inserted inside 'ietus' is 'IMPETUS'.
'of' acts as a link.
(Other definitions for impetus that I've seen before include "Momentum, stimulus" , "Motivation" , "influence" , "Force that moves something along" , "Driving force, forward movement" .)