expression
if it's ... then that's one thing, but ...; it's different when ... but
Used to contrast a hypothetical or specific case with a general situation. The pattern is often 'Aならともかく、Bは…' meaning 'If it were A, that would be one thing, but B is...'.
一度ならともかく、毎日遅刻するのは問題だ。
If it were just once, that would be one thing, but being late every day is a problem.
子供ならともかく、大人がそんなことをしてはいけない。
If it were a child, that would be one thing, but an adult shouldn't do such a thing.