I tend to agree with @Bill.French. What you’re trying to accomplish can be done within Airtable.
You can create views (one for each client) with only the fields that you require them to see and then share that view with them.
For example. Here is a full view of a sample Project Base. Notice all the clients and fields.
Now go and create a new view and customize it with only the fields that you would like your customer to see. Once complete, click on SHARE VIEW BUTTON from the tool bar, as seen in this image.
From there, I typically uncheck the ALLOW VIEWERS TO COPY DATA OUT OF THIS VIEW. What’s really important here is to not select the SHOW ALL FIELDS IN EXPANDED RECORDS.
Here’s the end result. This shows just one client, in this case Bigelow Tea and it only shows the fields that I left visible.
NOTE: VERY IMPORTANT: This view changes live and if you happen to be working in that view, and expand things (unhide fields), it will expand it for the client as well. So my recommendation is to create the view and leave it until such time that you want to remove it.