Illustrious celebrity entertaining the Spanish Left (7)
I believe the answer is:
stellar
'illustrious' is the definition.
(both can mean special or prominent)
'celebrity entertaining the spanish left' is the wordplay.
'celebrity' becomes 'star' (I've seen this before).
'entertaining' indicates putting letters inside.
'the spanish' becomes 'el' ('the' in Spanish).
'left' becomes 'l' (common abbreviation).
'el'+'l'='ell'
'star' enclosing 'ell' is 'STELLAR'.
(Other definitions for stellar that I've seen before include "High-class" , "Relating to the stars" , "Astral" , "celebrity" , "Like highlights" .)