Doubly outstanding damage? (6)
I believe the answer is:
deface
'damage?' is the definition.
(I've seen this in another clue)
'doubly outstanding' is the wordplay.
'doubly' becomes 'def' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'outstanding' becomes 'ace' (I've seen this before).
'def'+'ace'='DEFACE'
Can you help me to learn more?
(Other definitions for deface that I've seen before include "ruin" , "blemish" , "Deliberately spoil the appearance of something" , "Spoil or damage the surface of" , "Wantonly spoil the look of" .)