Above all (6)
'above all' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for mainly that I've seen before include "Chiefly, principally" , "For the most part" , "Generally or largely" , "Chiefly, largely" .)
(Other definitions for else that I've seen before include "Otherwise; different from" , "Other than (what is under consideration)" , "Besides, otherwise" , "In addition, besides" , "Adverb meaning if not, otherwise" .)