Disturb the thing set in stone (7)
I believe the answer is:
agitate
'disturb' is the definition.
(I've seen this before)
'the thing set in stone' is the wordplay.
'the thing' becomes 'it'.
'set in' indicates putting letters inside.
'stone' becomes 'agate' (I've seen this before).
'it' going within 'agate' is 'AGITATE'.
(Other definitions for agitate that I've seen before include "Make nervous; stir" , "Unsettle" , "Perturb" , "Stir up (trouble?)" , "Stir (up public opinion?)" .)