Dream location maybe, where you only get green lights? (4,2,3)
I believe the answer is:
land of nod
'dream location maybe' is the definition.
('in the Land of Nod' can mean asleep)
'you only get green lights?' is the wordplay.
I cannot quite see how this works, but
'get' could be 'land' (landing is a kind of getting) and 'land' is present in the answer.
This explanation may well be incorrect...
'where' acts as a link.
(Other definitions for land of nod that I've seen before include "Dropping-off place" , "Where Cain was banished after killing Abel" , "east of 27 [EDEN]" , "Where a murderer took refuge" , "Imaginary place of sleep" .)