:lisp-simple-1d-array is a foreign type which accepts a Lisp simple vector and passes a pointer to the first element of that vector.
The Lisp vector must be simple. That is, it does not have a fill pointer, is not adjustable, and it is not a displaced array.
The Lisp vector as subject to the same memory management restrictions as the array passed with :lisp-array. It must be statically allocated, and may need to be retained explicitly in Lisp.
The argument type, if non-nil, is a list (element-type &rest dimensions) and is used to check the element type and dimensions of the Lisp array passed.
LispWorks Foreign Language Interface User Guide and Reference Manual - 29 Sep 2017