This isn't an issue I've ever had, however a lag/compression drill which is essentially what you need here.
Grab an alignment stick off the internet or your nearest golf store. Then there's two parts of the drill depending on if you're casting early (top of swing) or late (near impact).
Early - Go to the top of the backswing, feel as though the alignment stick is pointing down towards the ground at the start of your downswing. Keep connected, then rotate through.
Late - Make half swings from address, feel is that the hands lead the club through impact, and you want the alignment stick to not hit your left side (assuming you're right handed) on the follow through, for this one you want the alignment stick to be sticking out a little further.
Both of these are drills, so not really feels you want to transfer to the course. Work through these with some 1/2 to 3/4 shots, then remove the training aid. Take some videos while doing the drill and compare them to so regular swings after. I'd imagine there are some videos of this drill on YouTube somewhere, they're quite widely used.
As bob said, this can become a technical nightmare so if the basic drills like this one aren't working, a good coach will have this ironed out in 1-2 30 minute sessions.