United Nations on average is prejudiced (6)
I believe the answer is:
unfair
'is prejudiced' is the definition.
(thesaurus)
'united nations on average' is the wordplay.
'united nations' becomes 'UN' (abbreviation).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'average' becomes 'fair' (synonyms).
'un'+'fair'='UNFAIR'
(Other definitions for unfair that I've seen before include "Unjust, partial" , "raining perhaps?" , "Swizz!" , "Not equitable or blond" , "Weighted" .)