Outstanding students covered by revised rates (7)
I believe the answer is:
stellar
'outstanding' is the definition.
(thesaurus)
'students covered by revised rates' is the wordplay.
'students' becomes 'll'.
'covered by' indicates putting letters inside.
'revised' is an anagram indicator.
'rates' with letters rearranged gives 'stear'.
'll' going inside 'stear' is 'STELLAR'.
(Other definitions for stellar that I've seen before include "of celebrities" , "Relating to the stars" , "Starry" , "Outstanding -- star-like" , "characteristic of The Sun, etc" .)