A riot on ground by the smallest great lake (7)
I believe the answer is:
ontario
'great lake' is the definition.
(I've seen this before)
'a riot on ground' is the wordplay.
'ground' indicates an anagram (grind the letters ).
'a'+'riot'+'on'='arioton'
'arioton' is an anagram of 'ONTARIO'.
'by the smallest' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
(Other definitions for ontario that I've seen before include "Most easterly Great Lake" , "Oration in Canadian province" , "one of the provinces" , "Canadian province and Great Lake" , "city" .)