Composer, after failing us, getting back the lead position (8)
I believe the answer is:
sullivan
'composer' is the definition.
(Sullivan is an example)
'failing us getting back the lead position' is the wordplay.
'failing' becomes 'ill'.
'getting back' is a reversal indicator.
'the lead position' becomes 'van'.
'ill'+'us'='illus'
'illus' in reverse letter order is 'sulli'.
'sulli'+'van'='SULLIVAN'
'after' acts as a link.
(Other definitions for sullivan that I've seen before include "Gilbert's partner" , "Sir 4 ---, composer" , "The S in G&S" , "Savoy Opera composer" , "Composer of music for Ruddigore, d. 1900" .)