devise, plan, deliberate, consul
惲 centers on mental activity aimed at creating or deciding: devising a plan, deliberating carefully, or consulting with others to reach a conclusion.
惲 combines 忄 (heart/mind) with 軍, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound related to mental activity.
The heart radical 忄 beside 軍 suggests a mind organizing thoughts like a military strategist: devising plans and deliberating carefully.
For ウン, imagine a general saying 'Un!' (うん, a grunt of approval) after devising a clever plan: the sound ウン cues the reading while the mind works.