Nasty words regularly preceding evidence of debts (6)
I believe the answer is:
odious
'nasty' is the definition.
(thesaurus)
'words regularly preceding evidence of debts' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'preceding' says to put letters next to each other.
'evidence of debts' becomes 'ious' (I've seen this in other clues).
The alternate letters of 'words' are 'od'.
'od'+'ious'='ODIOUS'
(Other definitions for odious that I've seen before include "Unequivocally detestable" , "Comparisons are said to be thus" , "Unpleasant, repulsive" , "offensive" , "Detestable, greatly disliked" .)