The whole matter (7)
I believe the answer is:
shebang
This could be a double definition.
'the whole' is the first definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'matter' is the second definition.
(shebang means any matter or situation)
Can you help me to learn more?
(Other definitions for shebang that I've seen before include "Whole affair" , "The entire system" , "The whole ___ (entirely)" , "Lot" , "affair in America" .)