The most common and most likely answer to this crossword clue is the 11 letter word INDENTATION
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More clues leading to the result INDENTATION
Buddy explains!

The straight part
We know that "Nick" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nick = indentation.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 INDENTATION mean?
INDENTATION noun- The act of indenting or state of being indented.
- A notch or recess, in the margin or border of anything
- A recess or sharp depression in any surface.
- The act of beginning a line or series of lines at a little distance within the flush line of the column or page, as in the common way of beginning the first line of a paragraph.
- A measure of the distance from the flush line
- A division unit of a piece of law distinguished by its indentation or by a dash