Rabble who are rioting, not acting to support society (6)
I believe the answer is:
shower
'rabble' is the definition.
(I've seen this before)
'who are rioting not acting to support society' is the wordplay.
'are rioting' indicates an anagram.
'not acting' becomes 'er' (I can't justify this - if you can you should give a lot more credence to this answer).
'to support' says to put letters next to each other (in a down clue, some letters hold others up).
'society' becomes 's' (common abbreviation in names of organisations).
'who' is an anagram of 'how'.
'how'+'er'='hower'
'hower' after 's' is 'SHOWER'.
(Other definitions for shower that I've seen before include "Person uncovering" , "Fluffy of rain" , "Sprinkle" , "awful group of people" , "detestable group" .)