what does this expression mean?

I think you may have omitted a word or two, because it doesn't seem to make sense grammatically, but it appears that VocalViews is agreeing to indemnify its client for any claims that may be made relating VocalFiews' right to the data with which it has provided its client.  I can't tell exactly what VocalViews' agreement is with its client, but if, for example, VocalViews is licensing a mailing list to the client, VocalViews is agreeing to indemnify the client if someone claims that the mailing list didn't belong to VocalViews, but rather to the person making the claim, and that therefore the client had to stop using it and/or pay the true owner for its use.  From the point of view of the client, I would be happier if the indemnification language were more specific and explicit:  "VocalViews hereby undertakes to indemnify and hold harmless Client for any and all damages or expenses incurred by Client as a result of any claim or dispute with any third paty (not including assignees or other successors in interest to VocalViews or Client) relating to VocalViews' acquisition and commercial use of the Data." - In this example, Data would be defined earlier in the agreement.