An improved worker? (6)
I believe the answer is:
fitter
'an improved worker?' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
This is the entire clue.
Can you help me to learn more?
(Other definitions for fitter that I've seen before include "Healthier" , "less likely to feel fatigue" , "Mechanic" , "Workman" , "better equipped" .)