Nine cats arranged in case (8)
I believe the answer is:
instance
'case' is the definition.
(synonyms)
'nine cats arranged' is the wordplay.
'arranged' indicates anagramming the letters.
'nine'+'cats'='ninecats'
'ninecats' anagrammed gives 'INSTANCE'.
'in' acts as a link.
(Other definitions for instance that I've seen before include "Case or example from ancients" , "Specimen" , "'Example, illustration (8)'" , "Example or single occurrence of something" , "Case in point" .)