The most common and most likely answer to this crossword clue is the 5 letter word FINAL
I've seen this crossword clue in The Guardian
F
I
N
A
L
More clues leading to the result FINAL
- Decisive female favoured by small boy
- Beef in a lasagne? Its potential selection is beyond dispute
- Terminal Five is not always ‘Ladies First’
- Last and first of file in a line
- Decisive force in Argyll vacated
- Ultimate bit of fluff in a leotard
- Decisive force in Argyll content to leave
- Last
- Last bit of fish? One left
- Decisive force in Arundel content to leave
Buddy explains!

The straight part
We know that "Last" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case last = final.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 FINAL mean?
FINAL noun- A final examination; a test or examination given at the end of a term or class; the test that concludes a class.
- The last round, game or match in a contest, after which the winner is determined.
- A contest that narrows a field of contestants (finalists) to ranked positions, usually in numbered places (1st place/prize, 2nd place/prize, etc.) or a winner and numbered runners-up (1st runner-up, etc.).
- The final part of a syllable, the combination of medial and rime in phonetics and phonology.
- The tonic or keynote of a Gregorian mode, and hence the final note of any conventional melody played in that mode.
- Last; ultimate.
- Conclusive; decisive.
- Respecting an end or object to be gained; respecting the purpose or ultimate end in view.
- (grammar) Expressing purpose; as in the term final clause.
- Word-final, occurring at the end of a word.