The most common and most likely answer to this crossword clue is the 5 letter word COSET
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More clues leading to the result COSET
Buddy explains!
The straight part
We know that "it’s added to and enlarges one like itself" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s added to and enlarges one like itself = coset.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 COSET mean?
COSET noun- The set that results from applying a group's binary operation with a given fixed element of the group on each element of a given subgroup.