Flighty animal in house of swine (6)
I believe the answer is:
scatty
'flighty' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?
'animal in house of swine' is the wordplay.
'animal' becomes 'cat' (I've seen this before).
'in' means one lot of letters goes inside another.
'house of swine' becomes 'sty' (I can't explain this - if you can you should believe this answer much more).
'cat' inserted into 'sty' is 'SCATTY'.
Can you help me to learn more?
(Other definitions for scatty that I've seen before include "miles away" , "Empty-headed" , "Informally crazy or feather-headed" , "Bird-witted" , "Crazy - in jazzy way?" .)