Sleep in Happy Valley? (9)
I believe the answer is:
dreamland
I believe this is a double definition.
'sleep' is the first definition.
(thesaurus)
'happy valley?' is the second definition.
(thesaurus)
'in' is the link.
(Other definitions for dreamland that I've seen before include "Utopia" , "Sleep; ideal world" , "Nod, perhaps" .)