Broadcaster busy putting out dangerous material (11)
I believe the answer is:
radioactive
'putting out dangerous material' is the definition.
'broadcaster busy' is the wordplay.
'broadcaster' becomes 'radio' (I've seen this before).
'busy' becomes 'active' ('active' can be similar in meaning to 'busy').
'radio'+'active'='RADIOACTIVE'
(Other definitions for radioactive that I've seen before include "Emitting dangerous particles" , "description of nuclear waste" , "hot" , "(Of elements) exhibiting spontaneous disintegration" , "period of decay?" .)