I'm a little confused about your question. However, i'll take a stab at what I surmise it to be.
You're cleared direct to XYZ. You chose DIR and the aircraft points itself in that direction. As you get closer, your aircraft begins to turn without actually flying over XYZ. Is this what you're talking about?
If so - and it's an Airbus - its due to the load factor (Rate) during the turn (Normal Law limits) from track to track.
If overflying XYZ is necessary, select the Over-Fly key. It will then over-fly XYZ, then it will perform a return to track manoeuvre after passing XYZ.