Tom's moustache is just the thing! (3,4,8)
I believe the answer is:
the cats whiskers
'thing' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'tom's moustache is just the' is the wordplay.
I cannot quite understand how this works, but
'tom's' could be 'cats' (a tom is a male cat) and 'cats' is found in the answer.
'is' is within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for the cats whiskers that I've seen before include "at least four whipping implements" , "item of early radio equipment?" , "Rectifiers" , "A belter" , "Superb - vibrissae" .)