Rampant disorder precipitated (12)
I believe the answer is:
unrestrained
'rampant' is the definition.
(thesaurus)
'disorder precipitated' is the wordplay.
'disorder' becomes 'unrest' (unrest is a kind of disorder**).
'precipitated' becomes 'rained' (raining is a kind of precipitating).
'unrest'+'rained'='UNRESTRAINED'
(Other definitions for unrestrained that I've seen before include "Wild" , "Unchecked" , "abandoned" , "spreading everywhere?" , "Not restricted" .)