The most common and most likely answer to this crossword clue is the 5 plus 4 letter word PENNY WISE
P
E
N
N
Y
W
I
S
E
More clues leading to the result PENNY WISE
Buddy explains!

The straight part
We know that "become careful with money" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case become careful with money = penny wise.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PENNY WISE mean?
PENNY WISE adjective- Thrifty in regards to small amounts of money.