Number ten having debts that are deleterious (7)
I believe the answer is:
noxious
'are deleterious' is the definition.
('noxious' can be a synonym of 'deleterious')
'number ten having debts' is the wordplay.
'number' becomes 'no' (abbreviation for 'number').
'ten' becomes 'x' (roman numeral).
'having' is a charade indicator (letters next to each other).
'debts' becomes 'ious'.
'no'+'x'+'ious'='NOXIOUS'
'that' acts as a link.
(Other definitions for noxious that I've seen before include "Unpleasant and harmful" , "Unwholesome" , "foul" , "Disgusting" , "Harmful to health" .)