This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
懧 combines 忄 (heart/mind) with 寧 (peaceful, rather), suggesting a meaning related to mental weakness or timidity, but the exact historical development is uncertain.
The heart radical 忄 beside 寧 (peaceful) suggests a heart that is too peaceful or yielding, perhaps weak or timid.
For ダ, imagine a weak heart going 'da' (ダ) with a faint beat, too timid to beat strongly.