They're on target to reform a sinner (6)
I believe the answer is:
inners
'they're on target' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'reform a sinner' is the wordplay.
'reform' is an anagram indicator (letters in a new form).
'sinner' with letters rearranged gives 'INNERS'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for inners that I've seen before include "Almost central target rings" , "Rings around the bull" .)