Broadcast wreckage of test car (7)
I believe the answer is:
scatter
'broadcast' is the definition.
(I've seen this before)
'wreckage of test car' is the wordplay.
'wreckage of' is an anagram indicator (I've seen this in other clues).
'test'+'car'='testcar'
'testcar' anagrammed gives 'SCATTER'.
(Other definitions for scatter that I've seen before include "Disperse, strew" , "Dissipate" , "Throw around; disperse" , "Spread" , "Strew randomly" .)