Formerly, quietly, one, a conservative, is acting in amendment for wrong (9)
I believe the answer is:
expiatory
'acting in amendment for wrong' is the definition.
I can't judge whether this defines the answer.
'formerly quietly one a conservative' is the wordplay.
'formerly' becomes 'ex' (prefix meaning former or onetime).
'quietly' becomes 'p' (p for piano and quiet).
'one' becomes 'i' (Roman numeral).
'conservative' becomes 'tory' (Tory means a member of the Conservative Party).
'ex'+'p'+'i'+'a'+'tory'='EXPIATORY'
'is' is the link.
Can you help me to learn more?
(Another definition for expiatory that I've seen is " Making atonement".)