Have a defender 110 that has started throwing the back end out when I take my foot of the accelerator, like it is crabbing and then the front swings out. Any ideas what is causing it.

I'm going looking at a P38 2.5 DSE AUTO on an S plate 1998. Any advice as to what I should be looking out for. My current vehicles are a defender 110 and 90 plus a series 3, so I know a bit about Land Rovers. But don't know much on Range Rovers. Any tips would be appreciated.