College is happily housing Japanese girl (6)
I believe the answer is:
geisha
'japanese girl' is the definition.
(I know this)
'college is happily housing' is the wordplay.
'housing' says the answer is hidden in the clue (part of the clue houses the answer).
'GEISHA' can be found hidden inside 'college is happily'.
(Other definitions for geisha that I've seen before include "Japanese paid companion" , "Entertainer in a kimono?" , "Japanese woman trained to please men" , "Japanese hostess who entertains men" , "A Japanese woman who entertains men" .)