The most common and most likely answer to this crossword clue is the 6 letter word MOMENT
I've seen this crossword clue in The Times
M
O
M
E
N
T
More clues leading to the result MOMENT
- Second turning point
- Second in importance
- Motorway sign might ultimately flash
- Second warning in case of misconduct
- See 11ac.
- Importance of sign in middle of mountain
- Fellows engaged in assessment of car professing importance
- Doctor’s intended not one to be flash
- Time when soldiers will get involved in test
- Second sign delivered in extremes of merriment
Buddy explains!

The straight part
We know that "Second/importance" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case second/importance = moment.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 MOMENT mean?
MOMENT noun- A brief, unspecified amount of time.
- The smallest portion of time; an instant.
- Weight or importance.
- The turning effect of a force applied to a rotational system at a distance from the axis of rotation.
- (unit) A definite period of time, specifically one-tenth of a point, or one-fortieth or one-fiftieth of an hour.
- A petit mal episode; such a spell.
- A fit; a brief tantrum.
- An infinitesimal change in a varying quantity; an increment or decrement.
- A quantitative measure of the shape of a set of points.