A major star’s alternative broadcast (6)

I believe the answer is:

altair

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'a major star's' is the definition.
'altair' can be an answer for 'star's' (Altair is a star in the constellation of Aquila). I am unsure of the 'a major' bit.

'alternative broadcast' is the wordplay.
'alternative' becomes 'alt' (I can't justify this - if you can you should believe this answer much more).
'broadcast' becomes 'air' (to air on TV).
'alt'+'air'='ALTAIR'

Can you help me to learn more?

(Other definitions for altair that I've seen before include "Member of Eagle family" , "Lariat (anag) - star in Aquila" , "Bright star; lariat (anag.)" , "A trial (anag) - star" , "Heavenly body" .)

I've seen this clue in The Independent.

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