What people are motivated to grind (4)
I believe the answer is:
axes
'motivated to grind' is the definition.
I can't judge whether this definition defines the answer.
'what people are' is the wordplay.
I cannot quite understand how this works, but
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is found in the answer.
The remaining letters 'xes' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for axes that I've seen before include "alliances" , "Cutting tools" , "X, Y scales on graph" , "guitars" , "Hatchets" .)