Cut wood conceals nothing (6)
I believe the answer is:
groove
'cut' is the definition.
(I've seen this before)
'wood conceals nothing' is the wordplay.
'wood' becomes 'grove' (a grove is a small wood).
'conceals' is an insertion indicator.
'nothing' becomes 'O' (looks like zero - 0).
'grove' going around 'o' is 'GROOVE'.
(Other definitions for groove that I've seen before include "Spiral track followed by a gramophone needle" , "'Channel, furrow (6)'" , "Long narrow cut or depression" , "Cut channel - set routine" , "Established routine" .)