Month preceding border chaos (6)
I believe the answer is:
mayhem
'chaos' is the definition.
(thesaurus)
'month preceding border' is the wordplay.
'month' becomes 'may' (May is an example).
'preceding' says to put letters next to each other.
'border' becomes 'hem' (I've seen this before).
'may'+'hem'='MAYHEM'
(Other definitions for mayhem that I've seen before include "Havoc, violent disturbance" , "Extreme disorder" , "Chaos, confusion, destruction" , "Pandemonium" , "Violent destruction of confusion" .)