A majestic glare perhaps (5)
I believe the answer is:
regal
'a majestic' is the definition.
(I know that majestic can be written as regal)
'glare perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'glare' anagrammed gives 'REGAL'.
(Other definitions for regal that I've seen before include "Grand and imposing" , "King's" , "fit for the Queen" , "Kingly or queenly" , "Fit for a monarch" .)