I put maze in new arrangement, including hint of rectangular shape (9)
I believe the answer is:
trapezium
'shape' is the definition.
(trapezium is a kind of shape)
'i put maze in new arrangement including hint of rectangular' is the wordplay.
'in new arrangement' indicates an anagram (I've seen this in other clues).
'including' means one lot of letters goes inside another.
'hint of' indicates taking the first letters.
The initial letter of 'rectangular' is 'r'.
'i'+'put'+'maze'='iputmaze'
'iputmaze' with letters rearranged gives 'tapezium'.
'tapezium' enclosing 'r' is 'TRAPEZIUM'.
(Other definitions for trapezium that I've seen before include "Geometric shape" , "Type of quadrilateral" , "Form of quadrilateral" , "Four-sided figure" , "Quadrilateral with two parallel sides of unequal length" .)