Hagar is horrible, keeps glaring (6)
I believe the answer is:
garish
'glaring' is the definition.
(thesaurus)
'hagar is horrible keeps' is the wordplay.
'keeps' says the answer is hidden in the clue.
'GARISH' is hidden in the letters of 'hagar is horrible'.
(Other definitions for garish that I've seen before include "Gaudy, lurid" , "Gaudy, showy" , "Gaudy, excessively bright" , "Gaudy, over-decorated" , "Gaudy, vulgarly bright" .)