Dark times when things go to pieces (6)
I believe the answer is:
nights
'dark times' is the definition.
(it's dark at night)
'things go to pieces' is the wordplay.
'go to pieces' indicates an anagram (I've seen 'going to pieces' mean this (going to pieces can mean breaking down)).
'things' is an anagram of 'NIGHTS'.
'when' acts as a link.
(Other definitions for nights that I've seen before include "dark times" , "Times of darkness" , "See 9" , "Times after sunset" , "Dark periods" .)