Outstanding organisation put up the cash (6)
I believe the answer is:
unpaid
'outstanding' is the definition.
('unpaid' can be similar in meaning to 'outstanding')
'organisation put up the cash' is the wordplay.
'organisation' becomes 'un' (UN is an example).
'put' says to put letters next to each other.
'up the cash' becomes 'paid' (I am not sure about this - if you are sure you should believe this answer much more).
'un'+'paid'='UNPAID'
Can you help me to learn more?
(Other definitions for unpaid that I've seen before include "Outstanding, owing" , "(Of debt) outstanding" , "Without wages" , "Of bill, outstanding" , "Not yet remunerated" .)