If you want to pay, up with it! (5)
I believe the answer is:
cough
'it' is the definition.
The definition suggests a singular noun which matches the answer.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for cough that I've seen before include "Noise from the throat" , "Throat infection" , "Throat complaint" , "Abrupt exhalation" , "Clear one's throat" .)