Initially cut, usually by even squares (5)
I believe the answer is:
cubes
'initially cut usually by even squares' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Maybe there's an association between them I don't understand?
'initially cut usually by even squares' is the wordplay.
'initially' indicates taking the first letters.
The first letters of 'cut usually by even squares' is 'CUBES'.
Can you help me to learn more?
(Other definitions for cubes that I've seen before include "1, 8, 27 etc" , "Solid body with six equal square faces" , "Three-dimensional shapes with six sides" , "die? More than one" , "Eg, eight, twenty-seven" .)