Inspirational leader isn't now failing … (7)
I believe the answer is:
winston
'inspirational leader' is the definition.
(Winston Churchill)
'isn't now failing' is the wordplay.
'failing' indicates anagramming the letters.
'isnt'+'now'='isntnow'
'isntnow' anagrammed gives 'WINSTON'.
(Other definitions for winston that I've seen before include "war leader" , "Statesman" , "11 [LAWMAKER]" , "-- Churchill, UK PM" , "Prime minister" .)