Extravagant faults we disguised (8)
I believe the answer is:
wasteful
'extravagant' is the definition.
('wasteful' can be similar in meaning to 'extravagant')
'faults we disguised' is the wordplay.
'disguised' indicates an anagram.
'faults'+'we'='faultswe'
'faultswe' with letters rearranged gives 'WASTEFUL'.
(Other definitions for wasteful that I've seen before include "Faults we consider being profligate" , "Extravagant" , "Prodigal" , "spendthrift" , "Uneconomical" .)