Animal in soup Mo's stirring (7)
I believe the answer is:
opossum
'animal' is the definition.
(opossum is a kind of animal)
'soup mo's stirring' is the wordplay.
'stirring' indicates an anagram.
'soup'+'mos'='soupmos'
'soupmos' anagrammed gives 'OPOSSUM'.
'in' acts as a link.
(Other definitions for opossum that I've seen before include "Small Australian marsupial" , "Large marsupial" , "American tree-dweller" , "Thick-furred marsupial of the Americas" , "American animal" .)