US broadcaster pinching round bum (4)
I believe the answer is:
hobo
'bum' is the definition.
('hobo' can be a synonym of 'bum')
'us broadcaster pinching round' is the wordplay.
'us broadcaster' becomes 'hbo' (US TV network).
'pinching' means one lot of letters goes inside another (taking inside).
'round' becomes 'o' (round can mean a round object).
'hbo' going around 'o' is 'HOBO'.
(Other definitions for hobo that I've seen before include "Tramp (US)" , "Homeless American" , "Vagrant, tramp" , "Itinerant" , "American tramp" .)