Array of postgraduate cheats, reportedly (6)
I believe the answer is:
matrix
'array' is the definition.
(matrix is a kind of array)
'postgraduate cheats reportedly' is the wordplay.
'postgraduate' becomes 'ma' (Master of Arts is a postgraduate degree).
'cheats reportedly' becomes 'trix' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ma'+'trix'='MATRIX'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for matrix that I've seen before include "Array of numbers in rows and columns" , "Rectangular array of quantities or symbols" , "table" , "A maths array in rows and columns" , "Mathematical arrangement of rows and columns" .)