In $entity variable, there is an object of same type as $other_address, but with all field values filled in.
I want to set all fields in $other_address object to hav
I'm not sure why cloning won't work.
This seems to work for me, at least in a basic test case:
$A = $em->find('Some\Entity',1);
$B = clone $A;
$B->setId(null);
If you've got relationships to worry about, you might want to safely implement __clone so it does what you want it to do with related entities.