Cats without a skin retreating inside, where they're never seen (6)
I believe the answer is:
crufts
'they're never seen' is the definition.
I know nothing about this answer so I can't tell whether this works.
'cats without a skin retreating inside' is the wordplay.
'without' suggests deleting specific letters.
'skin' becomes 'fur' (fur is a kind of skin).
'retreating' says the letters should be written backwards.
'inside' is an insertion indicator.
'cats' with 'a' taken out is 'cts'.
'fur' backwards is 'ruf'.
'cts' going around 'ruf' is 'CRUFTS'.
'where' is the link.
(Other definitions for crufts that I've seen before include "Annual London dog show" , "Annual international dog show" , "where there are lots of dogs" .)