How do I use unique_ptr in this scenario?

I have a problem with this code:

A* a = createAnAObject().get();

where createAnAObject() returns unique_ptr

the problem is that I have to do this:

x.setA(a);  

and the X object must have ownership of the A object, however, as I understand it, unique_ptr::get() creates a temporary object, which goes out of scope the next line and calls the destructor, deleting my A object?

What should I do? I cannot change the interface to the X object.