Great fun (but keep it dark?) (7)
I believe the answer is:
delight
'dark?' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Maybe there's a link between them I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for delight that I've seen before include "It could be Turkish" , "entrance?" , "Ecstasy" , "Extreme satisfaction" , "See 5" .)