Broadcast Scout Association's leaders' attempt (5)
I believe the answer is:
essay
'attempt' is the definition.
(essay can mean to try or attempt something)
'broadcast scout association's leaders'' is the wordplay.
'broadcast' shows a homophone (sound like) (how the word might sound on the radio or TV).
'leaders'' indicates taking the first letters (I've seen 'leaders' mean this).
The first letters of 'scout associations' is 'sa'.
'sa' is a homophone of 'ESSAY'.
(Other definitions for essay that I've seen before include "Make an effort to write one" , "Composition; attempt" , "Try - composition" , "Short treatise" , "Attempt - piece of writing" .)