The most common and most likely answer to this crossword clue is the 5 letter word SASSY
I've seen this crossword clue in The Times
S
A
S
S
Y
More clues leading to the result SASSY
- Cheeky American, for example, grabbing seconds
- Forward social security packs for one
- Impertinent fool stretches the bounds of stupidity
- Impudent fool in extremes of stupidity
- Impertinent reply about steamship
- American showing disrespect succeeded twice in speech
- Impertinent Neddy entering Seychelles
- Impertinent answer covering Saints
- Sigh audibly about fool giving lip
- Fresh chance to talk about shortstop
Buddy explains!

The straight part
We know that "Cheeky American" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cheeky american = sassy.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 SASSY mean?
SASSY adjective- Bold and spirited, cheeky, impudent, saucy.
- Somewhat sexy and provocative.
- Lively, vigorous.