Any ideas? I am working in a PAL 25fps timeline. I have one clip sent to me at the last minute that's NTSC 29.97.

How to I make it fit?

If you use the "search" feature here on the forum you'll find dozens of posts about this exact thing. Compressor has built-in settings for making the NTSC to PAL conversion (it's one of the most common conversions around) and if you read the other posts you'll find more detailed and optimal settings for making the conversions look their best.