Span within any riot (7)
I believe the answer is:
anarchy
'riot' is the definition.
(thesaurus)
'span within any' is the wordplay.
'span' becomes 'arch' (I've seen this in another clue).
'within' means one lot of letters goes inside another.
'arch' placed inside 'any' is 'ANARCHY'.
(Other definitions for anarchy that I've seen before include "without structure" , "State of civil disorder" , "Uncontrolled disorder" , "Society without government or law, chaos" , "Lawlessness; chaos" .)