Pay to go to a dance? He’s mad! (9)
I believe the answer is:
screwball
'he's mad' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'pay to go to a dance?' is the wordplay.
'pay' becomes 'screw' (I've seen this before).
'to go to' says to put letters next to each other.
'a dance?' becomes 'ball' (ball is a kind of dance).
'screw'+'ball'='SCREWBALL'
Can you help me to learn more?
(Other definitions for screwball that I've seen before include "odd fellow?" , "Eccentric" , "Crazy (person)" , "Freak" , "Card" .)