66a Be quiet! (For some whistling an order to be quiet) - I've got ?I?T, though wonder if I have 51d wrong - the clue is 'shed' and I've put 'lean to' but can't get it from the cryptic (cat catching insect in shed)
This one had me stumped, thought it was WIST, round here in W. Yorkshire when I was a kid 'wist thissen' meant shut up. Now can see that the answer is in the word whistling, you learn something every day!