Hill worker (3)
I believe the answer is:
ant
This could be a double definition.
'hill' is the first definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'worker' is the second definition.
(worker is a type of ant)
Can you help me to learn more?
(Other definitions for ant that I've seen before include "Little boy" , "Industrious insect" , "Small social insect" , "Termite" , "One working hard" .)