が先決

… is the priority

→ が

phrase Rare #43,211

… is the priority Follows the thing that should be dealt with or done first.

JA: まずは休むことが先決だ。

EN: Resting is the priority for now.

まずは村人を救うことが先決だ

First and foremost, we need to save the villagers.

— RRR (2022)

生きるのが先決

Staying alive comes first.

— イップ・マン序章 (2008)

君は煙草を吸うのをやめるのが先決だ。

Your first priority should be to quit smoking.