Where the bills are piling up (8)
I believe the answer is:
hoarding
'piling up' is the definition.
('hoard' can be a synonym of 'pile up')
'where the bills are' is the wordplay.
I cannot really understand how this works, but
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is located in the answer.
The remaining letters 'hording' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hoarding that I've seen before include "Board for ads" , "Collecting and keeping - large board for advertising" , "space for posters here?" , "Temporary screen, round a building site say" , "Large outdoor signboard" .)