\documentclass[varwidth]{standalone}
\usepackage{tikzlings}
\def\mylist{
bear/bears,
marmot/marmots,
pig/pigs%
}
\ExplSyntaxOn
% To be able to x-expand \iterateTikzlings, it has to be expandable, so
% no 'protected'. Also \clist_map_inline:Nn is not expandable, so we
% have to use \clist_map_function:NN instead.
\cs_new:Npn \tikzlings_iterate:N #1
{ \clist_map_function:NN #1 \__tikzlings_braced_items:n }
% \__tikzlings_braced_items:n will receive each clist item, then:
\cs_new:Npn \__tikzlings_braced_items:n #1