Magnificence makes Edgar run (8)
I believe the answer is:
grandeur
'magnificence' is the definition.
(I know that magnificence can be written as grandeur)
'makes edgar run' is the wordplay.
'makes' indicates anagramming the letters.
'edgar'+'run'='edgarrun'
'edgarrun' is an anagram of 'GRANDEUR'.
(Other definitions for grandeur that I've seen before include "Splendour or magnificence" , "Augustness" , "Impressive splendour" , "Magnificence - rare dung (anag)" , "Pomp" .)