Interrupt American quietly in broadcast (7)
I believe the answer is:
suspend
'interrupt' is the definition.
(suspending is a kind of interrupting)
'american quietly in broadcast' is the wordplay.
'american' becomes 'us'.
'quietly' becomes 'p' (p for piano and quiet).
'in' means one lot of letters goes inside another.
'broadcast' becomes 'send' ('send' can be a synonym of 'broadcast'**).
'us'+'p'='usp'
'usp' inserted into 'send' is 'SUSPEND'.
(Other definitions for suspend that I've seen before include "Dangle or postpone" , "Temporarily render inoperative" , "Sends up (anag)" , "Bring to a temporary halt" , "Interrupt" .)