Strange advert for debt (9)
I believe the answer is:
overdraft
'debt' is the definition.
(kind of debt)
'strange advert for' is the wordplay.
'strange' indicates anagramming the letters.
'advert'+'for'='advertfor'
'advertfor' with letters rearranged gives 'OVERDRAFT'.
(Other definitions for overdraft that I've seen before include "Bank facility to spend more than you have" , "Bank account deficit" , "figure in red?" , "Excess withdrawal from bank" , "Bank facility to go into the red" .)