Lawless venue for Olympics, in our opinion (7)
I believe the answer is:
riotous
'lawless' is the definition.
(thesaurus)
'venue for olympics in our opinion' is the wordplay.
'venue for olympics' becomes 'rio' (former Olympic host city Rio de Janeiro).
'in our opinion' becomes 'tous' (to us).
'rio'+'tous'='RIOTOUS'
(Other definitions for riotous that I've seen before include "Boisterous and unrestrained" , "Involving public disorder" , "Involving wild behaviour" , "Behaving wildly" , "Unrestrained, wild living perhaps" .)