Junior's cat is just about half dead (5)
I believe the answer is:
cadet
'junior's' is the definition.
(thesaurus)
'cat is just about half dead' is the wordplay.
'cat' becomes 'cad' (I can't justify this - if you can you should believe this answer much more).
'is just about' says the letters should be written in reverse (turned about or around).
'half' suggests halving the letters.
'dead' becomes 'late' (similar in meaning).
'late' halved is 'te'.
'te' reversed gives 'et'.
'cad'+'et'='CADET'
Can you help me to learn more?
(Other definitions for cadet that I've seen before include "recruit" , "Apprentice officer" , "Officer in training" , "Police or armed forces trainee" , "One in training" .)