Stuck on these few clues,would appreciate any help,thanks.
25 across- Pisano works,including one preparatory drawing(7)?IN????
31 across- Keeps bobbing head,endlessly donnish,excited about degree(7)???N?D?
18 down- Butcher bone in leg of mutton-thin cuts(7)?????MB
26 down- Where salmon nest? That is not seen in river swirls(5)???DS