The most common and most likely answer to this crossword clue is the 6 letter word ULTIMO
U
L
T
I
M
O
More clues leading to the result ULTIMO
- Extremely unusual to neglect going round last month
- April’s multimodal component
- Centre of Hull bypass drawn up last month
- Last month, university student overturned skip
- United, beginning to languish, fail to perform somersaults in September
- Cutback on fuel regularly in the last month
- University student’s leave rejected last month
Buddy explains!

The straight part
We know that "September" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case september = ultimo.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 ULTIMO mean?
ULTIMO adjective- On the last day (of a specified month).
- Of last month.