Sinatra cryptically leading line of stars! (6)

I believe the answer is:

astral

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'of stars' is the definition.
(relating to stars or astronomy)

'sinatra cryptically leading line' is the wordplay.
'sinatra cryptically' becomes 'astra' (I can't explain this - if you can you should give a lot more credence to this answer).
'leading' says to take the initial letters (the leading letter of the word).
The initial letter of 'line' is 'l'.
'astra'+'l'='ASTRAL'

Can you help me to learn more?

(Other definitions for astral that I've seen before include "Characteristic of stars" , "19 [STELLAR]" , "Starry sort of altars." , "like a star" , "Universal" .)

I've seen this clue in The Independent.

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