You can't build upon this karate qualification! (5,4)
I believe the answer is:
green belt
'you can't build upon this karate qualification' is the definition.
The definition suggests a singular noun which matches the answer.
This is the entire clue.
Can you help me to learn more?
(Other definitions for green belt that I've seen before include "Area of open land around a town where building is restricted" , "protected lung" , "status of karate?" , "Designated zone around town or city, preserved from development" , "Zone where development is banned (in theory)" .)