Splitting pieces of granite (7)
I believe the answer is:
tearing
'splitting' is the definition.
(I've seen this before)
'pieces of granite' is the wordplay.
'pieces of' is an anagram indicator (I've seen this in other clues).
'granite' with letters rearranged gives 'TEARING'.
(Other definitions for tearing that I've seen before include "violent" , "'Pulling apart, ripping (7)'" , "splitting" , "Granite (anag.)" .)