Are such shanks legs of mutton? (5)
I believe the answer is:
sheep
'mutton?' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for sheep that I've seen before include "Animals said to lack initiative" , "Ruminant animal" , "Dolly or Shaun" , "Woolly animal" , "Members of congregation" .)