Align only one text frame to baseline grid

What is the reason to have several text frames?  There are only few reasons to work with separate frames on the same page if you want to connect them anyway. 
As Scott wrote, baseline alignment is a text, not a frame property. You can align text to the baseline and in the next step fit the frame to the text. 

Aligning text to a grid is an attribute of the text, specifically it is a paragraph attribute. It is not an attribute of a text frame. If you want only the text in one frame to align to the baselin grid make sure the paragraph styles you use do not have that attribute turned on. Then either make a different style for the text in that frame or manually turn the attribute on in the Paragraph panel. You can do that by selecting the frame then turning the attribute on. If you have chained text frames and all the text is one paragraph for some reason then you will still have align to baseline grid on for all the text.