Rock turned up vermin (6)
I believe the answer is:
pumice
'rock' is the definition.
(I know that pumice is a type of rock)
'turned up vermin' is the wordplay.
'turned' is a reversal indicator.
'vermin' becomes 'mice'.
'up' back-to-front is 'pu'.
'pu'+'mice'='PUMICE'
(Other definitions for pumice that I've seen before include "Porous lava" , "Light form of solidified lava" , "Solidified lava used as an abrasive" , "Volcanic stone used as abrasive" , "Piece of volcanic rock used as an abrasive" .)