An instrument Edward desecrated (8)
I believe the answer is:
violated
'desecrated' is the definition.
(similar in meaning)
'an instrument edward' is the wordplay.
'an instrument' becomes 'viola' (viola is a kind of instrument).
'edward' becomes 'ted'.
'viola'+'ted'='VIOLATED'
(Other definitions for violated that I've seen before include "Treated irreverently or sacrilegiously" , "Defiled" , "Transgressed (rule)" , "Abused" , "Desecrated sacred place of dovetail." .)