Battle, as things going to pieces (8)
I believe the answer is:
hastings
'battle' is the definition.
(Hastings is an example)
'as things going to pieces' is the wordplay.
'going to pieces' indicates an anagram (going to pieces can mean breaking down).
'as'+'things'='asthings'
'asthings' with letters rearranged gives 'HASTINGS'.
(Other definitions for hastings that I've seen before include "Town in East Sussex" , "Not a good place for Harold" , "Ten sixty six battle" , "place of battle" , "Harold's objective?" .)