Totally twisted wood fences come down (8)
I believe the answer is:
collapse
'come down' is the definition.
(thesaurus)
'totally twisted wood fences' is the wordplay.
'totally' becomes 'all' (I've seen this in another clue).
'twisted' shows that the letters should be reversed in order.
'wood' becomes 'copse' (a copse is a small wood).
'fences' indicates putting letters inside (inserted letters are fenced off).
'all' backwards is 'lla'.
'lla' going into 'copse' is 'COLLAPSE'.
(Other definitions for collapse that I've seen before include "Sudden breakdown" , "Give way, fail suddenly" , "Faint and fall" , "Break-down or complete failure" , "Crumble" .)