It's bang out of order to support 500 idiots (8)
I believe the answer is:
dingbats
'idiots' is the definition.
Both the definition and answer are plural nouns.
Perhaps you can see an association between them that I don't see?
'it's bang out of order to support 500' is the wordplay.
'out of order' is an anagram indicator.
'to support' means one lot of letters go next to another (in a down clue, some letters hold others up).
'500' becomes 'D' (Roman numeral for 500).
'its'+'bang'='itsbang'
'itsbang' is an anagram of 'ingbats'.
'ingbats' after 'd' is 'DINGBATS'.
Can you help me to learn more?
(Another definition for dingbats that I've seen is " Typographical devices, such as an asterisk - (US) eccentrics".)