Answer is: You can't. Either the parent has overflow:hidden
then all child-elements will be clipped, or you have overflow:(visible|auto|scroll|...)
then all children are treated according to that rule. There is no possibility you could mix states - all children are treated equally.
However, you could introduce additional container-elements inside the parent (which no longer has overflow:hidden) like in this pseudo-code:
<parent>
<container1 style="overflow:hidden">
<!-- these will be clipped -->
<element>
<element>
</container>
<container2 style="overflow:visible">
<!-- these will be shown -->
<element>
<element>
</container>
</parent>
edit: example
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