How do I stop extending my left arm before contact?

I am a right-handed hitter and I am doing this thing where I would extend my left arm before contact, some people called that locking your arm. Others called it arm barring, but I think arm barring is when you extend before swinging. I am extending between when I start my swing and contact. I'm trying to stop doing this locking my arm thing, but it's not easy. It makes me hit weak ground and I can't get it out of the infield. So if you have any drills for that, that would be great.