Defile musical instrument with empty tune (7)
I believe the answer is:
violate
'defile' is the definition.
(thesaurus)
'musical instrument with empty tune' is the wordplay.
'musical instrument' becomes 'viola' (viola is a kind of musical instrument**).
'with' is a charade indicator (letters next to each other).
'empty' says to hollow out the word (remove centre letters).
'tune' with its centre taken out is 'te'.
'viola'+'te'='VIOLATE'
(Other definitions for violate that I've seen before include "Break (a rule)" , "Rudely disturb" , "Break in on; disregard" , "Profane" , "Contravene" .)