单打一

Traditional (Taiwan): 單打一

dāndǎyī ㄉㄢ ㄉㄚˇ ㄧ

    • to focus on one thing and ignore everything else

Character by character

Saying俗语俗語

Idiom惯用语 · Widely known

Literally
play one thing only
Meaning
To focus on one thing and ignore everything else. Mildly critical.

Sources