Redevelopment in old town starts civil disorder (4)
I believe the answer is:
riot
'civil disorder' is the definition.
'redevelopment in old town starts' is the wordplay.
'starts' suggests taking the first letters.
The first letters of 'redevelopment in old town' is 'RIOT'.
(Other definitions for riot that I've seen before include "Dazzling display - revelry" , "Rowdy behaviour" , "Civil disturbance" , "Ruckus, insurrection" , "Disturbance by unruly mob" .)