Make a Careless Mistake
This page is the CodyCross answer for the clue below from Casino, Group 280, Puzzle 2 (Billionaires).
Question is: Make a Careless Mistake
and the answer is: SLIPUP
Word Meaning:
SLIP UP — (idiomatic) To err, falter; to make a mistake, especially a seemingly small error.
Definitions from Wiktionary.