Rep intent on rewriting material (9)
I believe the answer is:
pertinent
'material' is the definition.
(I've seen this in another clue)
'rep intent on rewriting' is the wordplay.
'on' says to put letters next to each other.
'rewriting' indicates anagramming the letters.
'rep' put after 'intent' is 'intentrep'.
'intentrep' with letters rearranged gives 'PERTINENT'.
(Other definitions for pertinent that I've seen before include "fitting" , "Relevant, to the point" , "Apposite" , "Appropriate" , "Relevent, material" .)