The most common and most likely answer to this crossword clue is the 7 letter word SCALENE
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The straight part
We know that "made up of different sides" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case made up of different sides = scalene.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 SCALENE mean?
SCALENE noun- Any of several muscles extending from the neck to the first and second ribs.
- A scalene triangle.
- (of a triangle) Having sides unequal in length.