Glaring, senior relative in apartment (8)
I believe the answer is:
flagrant
'glaring' is the definition.
(thesaurus)
'senior relative in apartment' is the wordplay.
'senior relative' becomes 'gran' (I've seen this in other clues).
'in' is an insertion indicator.
'apartment' becomes 'flat' ('flat' can be a synonym of 'apartment').
'gran' placed into 'flat' is 'FLAGRANT'.
(Other definitions for flagrant that I've seen before include "Conspicuous, blatant" , "Shocking" , "Crying" , "Of unconcealed outrageousness" , "Barefaced" .)