Nice! 5a gave me a little trouble, and I'm still not sure which of "unusual" or "restricted" is the definition and which is the indicator - but I don't think either's a direct synonym to "rarer".
Cheers Connor. In 5a, unusual is the def. It's listed as a syn for rarer on thesaurus.com but granted, a less obvious one. The restricted is wordplay for taking just a bit of R-Rated, i.e. the double Rs
