Harebrained feline put in a pen (6)
I believe the answer is:
scatty
'harebrained' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I don't see?
'feline put in a pen' is the wordplay.
'feline' becomes 'cat' (cat is a kind of feline).
'put in' indicates putting letters inside.
'a pen' becomes 'sty' (both can mean an animal enclosure).
'cat' going within 'sty' is 'SCATTY'.
Can you help me to learn more?
(Other definitions for scatty that I've seen before include "Slangily crazy or scatterbrained" , "Crazy - in jazzy way?" , "Slightly unpredictable" , "Mentally disorganised and absent-minded" , "dizzy" .)