Ruined brass instrument has no depth (7)
I believe the answer is:
bungled
'ruined brass' is the definition.
The definition and answer can be both to do with social activities as well as being past participle verbs.
Perhaps you can see a link between them that I don't see?
'instrument has no depth' is the wordplay.
'instrument' becomes 'bugle' (bugle is a kind of instrument).
'has' means one lot of letters goes inside another.
'no' becomes 'n' (common abbreviation).
'depth' becomes 'd' (abbreviation in geometry).
'bugle' placed around 'n' is 'bungle'.
'bungle'+'d'='BUNGLED'
Can you help me to learn more?
(Other definitions for bungled that I've seen before include "Spoiled through incompetence" , "Slipped up there" , "mismanaged" .)