Happy taking flight in one's mind? (8)
I believe the answer is:
upstairs
'in one's mind?' is the definition.
Both the definition and answer are adverbs. Maybe you can see a link between them that I can't see?
'happy taking flight' is the wordplay.
'happy' becomes 'up' (I've seen this in other clues).
'taking' means one lot of letters go next to another.
'flight' becomes 'stairs' (I've seen this in another clue).
'up'+'stairs'='UPSTAIRS'
Can you help me to learn more?
(Other definitions for upstairs that I've seen before include "In the top half of a house" , "Mentally (colloquial)" , "On a higher floor" , "On the next floor" , "See 3" .)