甕中捉鱉

瓮中捉鳖
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

比喻舉手可得、確有把握。

重編國語辭典

Entry Composition

1 甕 wèng pottery container for water, wine etc
2 中 zhōng
  1. within; among; in
  2. middle; center
  3. while (doing sth); during
  4. (dialect) OK; all right
3 捉 zhuō
  1. to clutch
  2. to grab
  3. to capture
4 鱉 biē softshell turtle