In Alice in Wonderland, he couldn't quite build a theatre (6)
I believe the answer is:
hatter
'in alice in wonderland he couldn't quite build a theatre' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for hatter that I've seen before include "There's a mad one in 'Alice's Adventures in Wonderland'" , "Tea party participant (Alice)" , "Tea-party attender" , "There's a Mad one in 'Alice in Wonderland'" , "Threat (anag)" .)