British Prime Minister set up censor (5)
I believe the answer is:
bleep
'censor' is the definition.
(I've seen this in another clue)
'british prime minister set up' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'prime minister' becomes 'peel' (Robert Peel).
'set up' shows that the letters should be reversed in order.
'peel' in reverse letter order is 'leep'.
'b'+'leep'='BLEEP'
(Other definitions for bleep that I've seen before include "Electronic signal calling a person" , "Sharp electronic sound" , "Censor" , "High-pitched electrical signal" , "Short high tone as a signal or warning" .)