Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

What happens to a unit locked in combat at the beginning of a turn, which the enemy it is locked in combat with is wiped out during during the psychic phase (as smite has no restriction on targetting units locked in combat)?

Does the unit then shoot and charge as normal?

Yes, because in the Shooting Phase, you check again for enemy models in 1". If there are none, you can shoot.
Same for Charge Phase, you again check for enemy models in 1".

No such thing as "locked in combat" anymore.

If a unit is not within 1" of an enemy, you can select it to shoot. It doesn't matter how long it's been more than 1" away.

In short, yes, they shoot and charge as normal.