A tyro without fault (6)
I believe the answer is:
novice
'a tyro' is the definition.
(I know that tyro can be written as novice)
'without fault' is the wordplay.
'without' becomes 'no'.
'fault' becomes 'vice' (I've seen this before).
'no'+'vice'='NOVICE'
(Other definitions for novice that I've seen before include "Beginner, learner" , "New member (of religious order)" , "New starter" , "Salvage" , "Trainee monk" .)