Is my buxus tree dead?

[TracyJacks1]

I think I might already know the answer
It's been like this since early summer. Still a bit of green on it though

There is box blight around. Link shows how to recognise it.
perfectplants.co.uk/blog/box-blight-have-you-got-it-and-what-can-you-do
Or it might be due to needing water or something. A neighbour's box went brown but is now, a year or so later, going green but the brown is still visible.

You might as well cut back a lot of the dead foliage, it's no use where it is and it is shading out any possible new growth on the inner branches underneath. My suggestion would be to give it a haircut, take it out of the pot and plant it in the ground.