broaden, extend, expand, enlarge
擴 centers on making something wider or larger in scope: broadening, extending, expanding, or enlarging.
擴 is the traditional form of modern 拡. It combines 扌 (hand) with 廣, which likely contributes both sound and the idea of breadth or spaciousness, suggesting the action of spreading or widening by hand.
The hand radical 扌 beside 廣 (a shape associated with breadth) suggests using your hands to stretch something wide: broadening or expanding it.
For カク, imagine using your hands to expand a canvas tent: the canvas (カク) stretches wider as you pull.