French revolutionary leader leading honourable race (8)
I believe the answer is:
marathon
'race' is the definition.
(marathon is a kind of race)
'french revolutionary leader leading honourable' is the wordplay.
'french revolutionary leader' becomes 'marat' (Jean-Paul Marat).
'leading' is a charade indicator (letters next to each other).
'honourable' becomes 'hon' (as in Rt Hon, Right Honourable).
'marat'+'hon'='MARATHON'
(Other definitions for marathon that I've seen before include "Long and arduous" , "Footrace of approx 26 miles" , "Race of about 26 miles" , "Long run (with a wall to get through!)" , "Pheidippides' starting point" .)