There's not a lot of juice in one (4)
I believe the answer is:
cell
'lot of juice in one' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for cell that I've seen before include "Basic unit of living matter" , "Monastic room" , "Prisoner's accommodation" , "Small room for confining a prisoner" , "Animal or plant building unit" .)