City in revolt claiming this writer's flipping abrasive (6)
I believe the answer is:
pumice
'abrasive' is the definition.
(I've seen this before)
'city in revolt claiming this writer's flipping' is the wordplay.
'city' becomes 'EC' (the City of London postcode).
'in revolt' becomes 'up' (up can mean revolting or rioting).
'claiming' is an insertion indicator.
'this writer's' becomes 'i'm' ('I am' referring to the writer of the clue).
'flipping' shows that the letters should be reversed in order.
'ec'+'up'='ecup'
'ecup' going around 'im' is 'ecimup'.
'ecimup' backwards is 'PUMICE'.
(Other definitions for pumice that I've seen before include "Mineral" , "Porous lava" , "Volcanic stone used as abrasive" , "Light form of solidified lava" , "Solidified lava used as an abrasive" .)