Clue: A poor worker holding in hand sandpaper? (8)
Answer: ABRADANT
Explanation: Definition: sandpaper?
 [A + BAD(poor/of a low standard) + ANT(a social insect, one who could belong to the worker caste) ] **containing**(holding in) R(abbrev. for "right"/the hand opposed to the left, as with "a boxer's right").
Defn: Of which sandpaper is an example/?.