瓮中捉鳖

甕中捉鱉
wèngzhōngzhuōbiē
  1. lit. to catch a turtle in a jar (idiom)
  2. fig. to go after easy prey

CEDICT

to catch or arrest a target already within one's grasp (and cannot escape)

Wiktionary

比喻举手可得有把握

重編國語辭典

Entry Composition