Hazel's relative holds English manuscript back to damage someone's reputation (8)
I believe the answer is:
besmirch
'to damage someone's reputation' is the definition.
I can't judge whether this definition defines the answer.
'hazel's relative holds english manuscript back' is the wordplay.
'hazel's relative' becomes 'birch' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'holds' means one lot of letters goes inside another.
'english' becomes 'e' (abbreviation).
'manuscript' becomes 'ms' ('ms' can be a synonym of 'manuscript').
'back' shows that the letters should be reversed in order.
'ms' written backwards gives 'sm'.
'e'+'sm'='esm'
'birch' going around 'esm' is 'BESMIRCH'.
Can you help me to learn more?
(Other definitions for besmirch that I've seen before include "Sully" , "dull" , "Damage (a reputation)" , "Foul" , "run down" .)