The most common and most likely answer to this crossword clue is the 14 letter word MULTIPLICATIVE
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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 MULTIPLICATIVE mean?
MULTIPLICATIVE noun- (grammar) A grammatical adverbial case in Finnish.
- Of or pertaining to multiplication.
- (of a function, etc.) Distributive over multiplication.
- Having multiplication as an operator.