Broadcast end of 'open sesame' as a group (2,5)
I believe the answer is:
en masse
'as a group' is the definition.
('en masse' can be a synonym of 'as a group')
'broadcast end of open sesame' is the wordplay.
'broadcast' indicates anagramming the letters.
'end of' suggests the final letters.
The last letter of 'open' is 'n'.
'n'+'sesame'='nsesame'
'nsesame' with letters rearranged gives 'EN MASSE'.
(Other definitions for en masse that I've seen before include "Sees man (anag.)" , "Many as one" , "All together as a group" , "All together - in France (2.5)" , "All together (Fr.)" .)