1A Alternatively sited in branch town ?O?O???
3D What man needs to cope ??? - middle letter is penultimate letter of previous clue.
13D Committed to substitute position indeed! ?E?U?E?
20D The law has one, too, to shoulder ?R?and I suspect this is arm.
Thanks Bibblebub - I suspected it was "or" in a synonym for limb, but could I think of it? Also on the right lines of "deed" for 13D, but failing absolutely to get "put".