A poor worker holding in hand sandpaper? (8)
I believe the answer is:
'sandpaper?' is the definition.
(sandpaper is a kind of abradant)
'a poor worker holding in hand' is the wordplay.
'poor' becomes 'bad' (similar in meaning).
'worker' becomes 'ant' (worker is a type of ant).
'holding in' is an insertion indicator.
'hand' becomes 'R' (abbreviation for right, as in the right-hand side).
'badant' enclosing 'r' is 'bradant'.
(Other definitions for abradant that I've seen before include "eroding" , "scratchy type?" , "grating" , "wearing away" .)