Stop sibling cutting precious stone (8)
I believe the answer is:
abrogate
'stop' is the definition.
(I've seen this before)
'sibling cutting precious stone' is the wordplay.
'sibling' becomes 'bro' (I've seen this before).
'cutting' is an insertion indicator (some letters cut their way into a word).
'precious stone' becomes 'agate' (I've seen this before).
'bro' going into 'agate' is 'ABROGATE'.
(Other definitions for abrogate that I've seen before include "Do away with" , "Abolish formally" , "Formally cancel (an agreement)" , "Cancel or repeal, say a law" , "Get rid of" .)