Lean is an agile technique
Crystal, DSDM, XP, Scrum, RUP, Lean etc... are all frameworks as such, they are all techniques. The problems come in agile when people say "i'm agile because I do Scrum" or "i'm agile because I do lean", the whole point of agile and why it came about was to bring together all these different techniques, see what was common, come up with a set of tenets that fit across the whole spectrum, and make sure that when you create something, you stick to the core beliefs* but everything else is flexible.
I have never recommended to anyone that they do Scrum or Lean or XP (which for where I work is slightly ironic
), what I do recommend is to look at the situation you are in, look at the tools you have available and do they best thing in your situation. Pick something from every technique out there if you like, if it works for you, then that is the ideal solution
I find it amusing when consultancies come into a company and say "To be agile, you must follow this process!"
*http://agilemanifesto.org/principles.html
This is what agile is, anything else is just smoke and mirrors.