The most common and most likely answer to this crossword clue is the 6 letter word COLOUR
I've seen this crossword clue in Financial Times
C
O
L
O
U
R
More clues leading to the result COLOUR
- Erroneously perceiving screen after firm, stern glance
- State of Denver to look threatening – black?
- Pass over the Guardian’s prejudice
- Oddly, only the Guardian’s after first instalment of Camberwick Green?
- Pass over, in the end, to you for characteristic ambience
- Short, lofted shot landing 25? Almost blush
- Firm scowl causes blush
- Detained by tribunal interminably, see red?
- After poisonous gas, look black and go red
- Standard appearance
Buddy explains!

The straight part
We know that "blush" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case blush = colour.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 COLOUR mean?
COLOUR noun- The spectral composition of visible light
- A subset thereof:
- A paint.
- Human skin tone, especially as an indicator of race or ethnicity.
- Skin color, noted as normal, jaundiced, cyanotic, flush, mottled, pale, or ashen as part of the skin signs assessment.
- A flushed appearance of blood in the face; redness of complexion.
- Richness of expression; detail or flavour that is likely to generate interest or enjoyment.
- A standard, flag, or insignia:
- (in the plural) An award for sporting achievement, particularly within a school or university.
- (in the plural) The morning ceremony of raising the flag.
- A property of quarks, with three values called red, green, and blue, which they can exchange by passing gluons.
- A third-order measure of derivative price sensitivity, expressed as the rate of change of gamma with respect to time, or equivalently the rate of change of charm with respect to changes in the underlying asset price.
- The relative lightness or darkness of a mass of written or printed text on a page. (See type color.)
- Any of the colored balls excluding the reds.
- A front or facade; an ostensible truth actually false; pretext.
- An appearance of right or authority; color of law.
- To give something color.
- To apply colors to the areas within the boundaries of a line drawing using colored markers or crayons.
- (of a person or their face) To become red through increased blood flow.
- To affect without completely changing.
- To attribute a quality to; to portray (as).
- To assign colors to the vertices of a graph (or the regions of a map) so that no two vertices connected by an edge (regions sharing a border) have the same color.
- Conveying color, as opposed to shades of gray.