Pen a volume in fury? That's Harry! (6)
I believe the answer is:
ravage
'that's harry' is the definition.
(synonyms)
'pen a volume in fury?' is the wordplay.
'pen a volume' becomes 'va' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'fury?' becomes 'rage' (synonyms).
'va' put into 'rage' is 'RAVAGE'.
Can you help me to learn more?
(Other definitions for ravage that I've seen before include "Lay waste, plunder" , "Act like a 6" , "Wreak havoc upon" , "Cause extensive destruction" , "Devastation" .)