Disturb it splitting stone (7)
I believe the answer is:
agitate
'disturb' is the definition.
(I know that disturb can be written as agitate)
'it splitting stone' is the wordplay.
'splitting' is an insertion indicator.
'stone' becomes 'agate' (I've seen this before).
'it' put into 'agate' is 'AGITATE'.
(Other definitions for agitate that I've seen before include "Fluster" , "'Stir, excite (7)'" , "Disturb, cause to worry" , "Perturb" , "Get upset" .)