The most common and most likely answer to this crossword clue is the 10 letter word ABERRATION
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result ABERRATION
- Planning a near orbit must be an anomaly
- Be gripped by storytelling, ignoring initial irregularity
- Ear to brain, extraordinary lapse
- President helping to cover up Republican’s deviancy
- Right to stop allowance after Lincoln’s moral lapse
- Peculiarity of a train bore rambling
- Flying airborne, taking in a tense deviation from course
- Anomaly of hesitation by sailor with allowance
- President runs, with allowance for lapse
- Straying, sailor helping to keep direction right
Buddy explains!

The straight part
We know that "deviation from course" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deviation from course = aberration.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 ABERRATION mean?
ABERRATION noun- The act of wandering; deviation from truth, moral rectitude; abnormal; divergence from the straight, correct, proper, normal, or from the natural state.
- The convergence to different foci, by a lens or mirror, of rays of light emanating from one and the same point, or the deviation of such rays from a single focus; a defect in a focusing mechanism that prevents the intended focal point.
- A small periodical change of position in the stars and other heavenly bodies, due to the combined effect of the motion of light and the motion of the observer.
- A partial alienation of reason.
- A mental disorder, especially one of a minor or temporary character.
- Atypical development or structure; deviation from the normal type; an aberrant organ.
- A deviation of a tissue, organ or mental functions from what is considered to be within the normal range.