Disturbance after prisoners start to trash building (12)
I believe the answer is:
construction
'building' is the definition.
(I've seen this before)
'disturbance after prisoners start to trash' is the wordplay.
'disturbance' becomes 'ruction' (ruction is a kind of disturbance**).
'after' means one lot of letters go next to another.
'prisoners' becomes 'cons'.
'start to' says to take the initial letters.
The initial letter of 'trash' is 't'.
'cons'+'t'='const'
'ruction' after 'const' is 'CONSTRUCTION'.
(Other definitions for construction that I've seen before include "Building; interpretation" , "Industry of erecting buildings" , "Act of building" , "Process of erecting buildings" .)