Energy equals discharged voltage doubled, divided by resistance (5)
I believe the answer is:
verve
'energy' is the definition.
(verve is a kind of energy)
'discharged voltage doubled divided by resistance' is the wordplay.
'discharged' says to hollow out the word (remove centre letters) (the letters inside the word released or discharged).
'doubled' says to double the letters.
'divided by' is an insertion indicator.
'resistance' becomes 'r' (electronics abbreviation).
'voltage' with its centre taken out is 've'.
've' doubled is 'veve'.
'veve' going around 'r' is 'VERVE'.
'equals' acts as a link.
(Other definitions for verve that I've seen before include "Life" , "Sparkling enthusiasm" , "Dashing enthusiasm" , "Gusto; energy" , "Sparkle" .)