This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 竨 is uncertain. It visually combines 立 and 卓, but the original semantic or phonetic role of these components is unclear.
Since the meaning is unclear, picture a tall (立) and outstanding (卓) figure standing alone, representing something lofty or obscure.
For チョウ, imagine a tall, outstanding chief named Chou standing alone: Chou -> チョウ, matching the kanji's lofty appearance.