Practise using eraser he replaced (8)
I believe the answer is:
rehearse
'practise' is the definition.
(I know that practise can be written as rehearse)
'eraser he replaced' is the wordplay.
'replaced' is an anagram indicator.
'eraser'+'he'='eraserhe'
'eraserhe' with letters rearranged gives 'REHEARSE'.
'using' is the link.
(Other definitions for rehearse that I've seen before include "Practice in theatre" , "What actor does to prepare for play" , "Run through (a play)" , "Cast practise for play" , "Practise - run through" .)