Educated miners on energy charge (8)
I believe the answer is:
numerate
'educated' is the definition.
('numerate' can be similar in meaning to 'educated')
'miners on energy charge' is the wordplay.
'miners' becomes 'num'.
'on' means one lot of letters go next to another.
'energy' becomes 'e' (physics symbol as in E=mca).
'charge' becomes 'rate' (rate is a kind of charge**).
'num'+'e'+'rate'='NUMERATE'
(Other definitions for numerate that I've seen before include "Able to understand figures" , "Well versed in maths" , "Good with figures" , "Able to work with numbers - tell" , "Mathematically able" .)