What? Type declarations in CL (which came from prior Lisp dialects) were added, so that optimizing Lisp compilers can use those to create fast machine code on typical CPUs (various CISC and RISC processors). Several optimizing compilers have been written, taking advantage of that feature. The compiler of SBCL would be an example. SBCL (and CMUCL before that) also uses type declarations as assertions. So, both the SBCL runtime and the SBCL compiler use type declarations.
> why then it can't be 'hosted' like Clojure?
ABCL does not exist?