Break provided in case of riot (4)
I believe the answer is:
rift
'break' is the definition.
(thesaurus)
'provided in case of riot' is the wordplay.
'provided' becomes 'if'.
'in' indicates putting letters inside.
'case of' says to hollow out the word (remove centre letters) (outsides of).
'riot' with its centre taken out is 'rt'.
'if' placed within 'rt' is 'RIFT'.
(Other definitions for rift that I've seen before include "cleavage" , "Cleft in earth or breach in relationship (4)" , "Cleft or fissure" , "Breach, rupture" , "Serious falling out" .)