Tesla, say, on electronic charge (4)
I believe the answer is:
care
'charge' is the definition.
(synonyms)
'tesla say on electronic' is the wordplay.
'tesla say' becomes 'car' (I am not sure about this - if you are sure you should believe this answer much more).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'electronic' becomes 'e' (as in e-mail or e-books).
'car'+'e'='CARE'
Can you help me to learn more?
(Other definitions for care that I've seen before include "Prudence" , "Protective custody" , "See 16" , "Have concern or regard" , "Happy-go-lucky" .)