My cat has no tail, or body (6)
I believe the answer is:
corpus
'body' is the definition.
(I've seen this before)
'my cat has no tail' is the wordplay.
'my' becomes 'cor' (both are expressions of surprise).
'cat' becomes 'puss' (puss is a kind of cat).
'has no tail' means to remove the last letter.
'puss' with its last letter removed is 'pus'.
'cor'+'pus'='CORPUS'
'or' acts as a link.
(Other definitions for corpus that I've seen before include "The entire works of a writer" , "Collection of works by one writer" , "collection of literature" , "Body (of work etc)" , "A body as of writings" .)