Writing material, hack with term for Professional Foul (5)
I believe the answer is:
chalk
'writing material' is the definition.
(I've seen this in another clue)
'hack with term for professional foul' is the wordplay.
'with' is a charade indicator (letters next to each other).
'term for' suggests the final letters (the letter which terminates the word).
'foul' is an anagram indicator.
The last letter of 'professional' is 'l'.
'hack' after 'l' is 'lhack'.
'lhack' with letters rearranged gives 'CHALK'.
(Other definitions for chalk that I've seen before include "Substance totally different from cheese!" , "Opposite of cheese?" , "Soft white rock used for writing on boards etc" , "Calcium carbonate" , "Soft white limestone (as distinct from cheese)" .)