One stopping nonsense causes disorder (4)
I believe the answer is:
riot
'disorder' is the definition.
(I know that riot is a type of disorder)
'one stopping nonsense' is the wordplay.
'one' becomes 'i' (Roman numeral).
'stopping' is an insertion indicator (stopping can mean blocking a gap).
'nonsense' becomes 'rot' (rot can mean nonsense or rubbish).
'i' put inside 'rot' is 'RIOT'.
'causes' acts as a link.
(Other definitions for riot that I've seen before include "Run amok" , "Take to the streets" , "Debauchery" , "Unruly assembly" , "loose living" .)