broaden, extend, expand, enlarge
拡 centers on making something larger in scope or size: broadening, extending, expanding, or enlarging.
拡 is the modern simplified form of 擴. The older form combines 扌 (hand) with 廣, which likely contributed the sound and the idea of spreading or widening by hand.
The left hand 扌 beside 広 (wide) suggests using your hands to make something wider: broadening or expanding it.
For カク, imagine using your hands to expand a canvas: canvas -> カク, and the hand stretches it wider.
expansion; extension
spreading; disseminating; scattering
expansion; extension; enlargement
expansion
voice amplification
military expansion; arms buildup
magnifying glass; magnifier; loupe
widening (of a road)
sales expansion; increase in sales
address field extension
code extension character
Streaming SIMD Extensions; SSE
spread spectrum communication
filename extension
file extension
(web) browser extension
(web) browser extension
memory expansion card
memory expansion board
nonexpansion; localization; localisation; nonaggravation