Little creature very hard on Adam (3)
I believe the answer is:
ant
This clue might be a double definition.
'little creature' is the first definition.
'hard on adam' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'very' is the link.
Can you help me to learn more?
(Other definitions for ant that I've seen before include "Colonial insect?" , "that may be a soldier" , "The insect lives in a social colony" , "Hill-dweller" , "one living in colonies" .)