Reverse boat with gear change (8)
I believe the answer is:
abrogate
'reverse' is the definition.
(thesaurus)
'boat with gear change' is the wordplay.
'with' means one lot of letters go next to another.
'change' indicates anagramming the letters.
'boat'+'gear'='boatgear'
'boatgear' with letters rearranged gives 'ABROGATE'.
(Other definitions for abrogate that I've seen before include "Cancel or repeal, say a law" , "Get a boar to annul" , "Do away with" , "Annul - to a barge (anag)" , "Rescind" .)