Energy Tesla understood (3)
I believe the answer is:
got
'understood' is the definition.
(getting is a kind of understanding)
'energy tesla' is the wordplay.
'energy' becomes 'go' (go can mean energy or enthusiasm).
'tesla' becomes 'T' (scientific unit).
'go'+'t'='GOT'
(Other definitions for got that I've seen before include "Received; understood" , "Caught" , "came by" , "Acquired" , "Landed" .)