Pleasing arrangement that doesn't change on reflection? (8)
I believe the answer is:
symmetry
'pleasing arrangement' is the definition.
'symmetry' can be an answer for 'arrangement' (thesaurus). I am unsure of the 'pleasing' bit.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for symmetry that I've seen before include "Mirrored disposition about axis" , "Arrangement of parts in pleasing proportions" , "Regularity of shape" , "Proportion; beauty of form" , "Balance between two parts" .)