Asian language restriction in broadcast (4)
I believe the answer is:
thai
'asian language' is the definition.
(language of Thailand)
'restriction in broadcast' is the wordplay.
'restriction' becomes 'tie'.
'in broadcast' indicates a 'sounds like' (homophone) clue.
'tie' sounds like 'THAI'.
(Other definitions for thai that I've seen before include "oriental language" , "A hit (anag)" , "Native of Southeast Asia" , "Someone from Bangkok, perhaps" , "Coming from Bangkok?" .)