The most common and most likely answer to this crossword clue is the 6 letter word PERIOD
I've seen this crossword clue in The Daily Telegraph
P
E
R
I
O
D
More clues leading to the result PERIOD
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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.
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What does PERIOD mean?
PERIOD noun- A length of time.
- A period of time in history seen as a single coherent entity; an epoch, era.
- The punctuation mark “.” (indicating the ending of a sentence or marking an abbreviation).
- The length of time during which the same characteristics of a periodic phenomenon recur, such as the repetition of a wave or the rotation of a planet.
- Female menstruation.
- A section of an artist's, writer's (etc.) career distinguished by a given quality, preoccupation etc.
- Each of the divisions into which a school day is split, allocated to a given subject or activity.
- Each of the intervals into which various sporting events are divided.
- The length of time for a disease to run its course.
- An end or conclusion; the final point of a process etc.
- A complete sentence, especially one expressing a single thought or making a balanced, rhythmic whole.
- A specific moment during a given process; a point, a stage.
- A row in the periodic table of the elements.
- A subdivision of an era, typically lasting from tens to hundreds of millions of years, see Appendix: Geologic timescale.
- A Drosophila gene, the gene product of which is involved in regulation of the circadian rhythm.
- Two phrases (an antecedent and a consequent phrase).
- The length of an interval over which a periodic function, periodic sequence or repeating decimal repeats; often the least such length.
- End point, conclusion.
- To come to a period; to conclude.
- To put an end to.
- Designating anything from a given historical era.
- Evoking, or appropriate for, a particular historical period, especially through the use of elaborate costumes and scenery.
- That's final; that's the end of the matter (analogous to a period ending a sentence); end of story