Delightful, but damaging to 100 (8)
I believe the answer is:
charming
'delightful' is the definition.
(I've seen this before)
'damaging to 100' is the wordplay.
I cannot really understand how this works, but
'100' could be 'c' (Roman numeral) and 'c' is found in the answer.
The remaining letters 'harming' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'but' acts as a link.
Can you help me to learn more?
(Other definitions for charming that I've seen before include "Lovely! - with 15a" , "Delightful, attractive" , "Beguiling, enchanting" .)