Posted: 30/10/2015 at 09:28
It looks like an elder to me - we can have a stab at saying which one when it grows new leaves next spring.
In the meantime I'd cut every branch hard back to about 18" from the ground. That will give the roots less plant to support. If you can feel natural joints in the stems - a slight swelling where new shoots form - cut back to about an inch above one which is about 18" above soil level. If you can't feel the joints don't worry about them at this stage. Just cut the branches back to 18".
And don't water it any more. It's leaves are falling - that's perfectly natural for this time of year - so it really doesn't need watering - the winter rains will be enough, and the roots also need oxygen - too much water will 'drown' them.
Elder are pretty tough plants - don't panic - there's a very good chance it'll survive . Good luck