The most common and most likely answer to this crossword clue is the 15 letter word RATIONALISATION
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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.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does RATIONALISATION mean?
RATIONALISATION noun- The process, or result of rationalizing.
- A statement of one's motives, or of the causes of some event.
- A reorganization of a company or organization in order to improve its efficiency.
- The concealment of true motivation in some non-threatening way.
- The simplification of an expression without changing its value.