I'll assume the wing is on straight... (major assumption... easy to have it crooked)

Does the plane also tend to want to dive a little?
If so, slightly bend the pushrod for the right taileron/ruddervator (whatever you want to call it...) to bring that control srface up a LITTLE. This gives a little up and a little right.

Does the plane want to climb as it turns left? Bend the left ushrod to make the left taileron deflect don a little. That gives both down and right.

If it tries to hold altitude... you need to do BOTH of the above EVENLY.

If you can't do it by bend-adjusting the pushrods... I'll have to see a picture of the control lnks to tell you better how to fix it. It CAN be fixed.