Shun riotous region (6)
I believe the answer is:
ignore
'shun' is the definition.
'riotous region' is the wordplay.
'riotous' indicates anagramming the letters.
'region' anagrammed gives 'IGNORE'.
(Other definitions for ignore that I've seen before include "Give no attention to" , "Deliberately take no notice" , "Send to Coventry" , "Slight" , "Discount" .)