Silly cat among pigs? (6)
I believe the answer is:
scatty
'silly' is the definition.
(scatty means silly or absent-minded)
'cat among pigs?' is the wordplay.
'among' indicates putting letters inside (inserted letters are placed among others).
'pigs?' becomes 'sty' (as in a pig sty).
'cat' going into 'sty' is 'SCATTY'.
(Other definitions for scatty that I've seen before include "Mentally disorganised and absent-minded" , "Crazy - in jazzy way?" , "Feather-brained" , "Informally crazy or feather-headed" , "Bird-witted" .)