Where Arthur turned up a great deal (7)
I believe the answer is:
camelot
'where arthur' is the definition.
The definition suggests a singular noun which matches the answer.
'turned up a great deal' is the wordplay.
'turned up' becomes 'came'.
'a great deal' becomes 'lot' ('lot' can be a synonym of 'great deal').
'came'+'lot'='CAMELOT'
Can you help me to learn more?
(Other definitions for camelot that I've seen before include "mythical place" , "King Arthur's court - or JFK's" , "royal court" , "Fabulous city" , "Idyllic situation" .)