The tooth next to a root canal is now loose. i think it may have been from the dam clip. will it improve?

Hopefully: this is not uncommon after dental manipulation; however you must consult the dentist who performed the root canal.

Yes it should: if the mobility of the tooth was caused by the rubber dam clamp then it should tighten up in a day or two.

Not from clamp: if an adjacent tooth is loose, then it needs to be evaluated! It is not from a rubber dam clamp!

Not likely: The clamps and dam can cause a damage when placed on teeth that are poorly shaped, partially erupted or severely decayed, but not to the adjacent tooth. See your dentist for post-op evaluation.

Depends: Isolation of a tooth during root canal is commonly accomplished with a rubber dam. This is usually secured with a clamp on the tooth being treated. It is uncommon for it to effect the tooth adjacent to it. If the clamp was placed on the adjacent tooth being treated it is still uncommon for it to cause it to become loose. I suggest you return to your DDS to re-evaluated your problem.

Yes: Yes, if the tooth was previously stable, it should tighten up.