Industrious worker's endless complaint (3)
I believe the answer is:
bee
'industrious worker's' is the definition.
'bee' can be an answer for 'worker's' (a worker bee). I'm not sure about the 'industrious' bit.
'endless complaint' is the wordplay.
'endless' means to remove the last letter.
'complaint' becomes 'beef' (beef can mean a complaint or objection).
'beef' with its final letter removed is 'BEE'.
Can you help me to learn more?
(Other definitions for bee that I've seen before include "In one's bonnet, it's a persistent idea" , "Social worker possibly" , "Hymenopterous insect" , "Four-winged insect" , "Hairy-bodied insect" .)