In using a standard form of power (3)
I believe the answer is:
gas
'power' is the definition.
(I've seen this in another clue)
'in using a standard form' is the wordplay.
'in' indicates a hidden word.
'GAS' is hidden within 'using a standard form'.
'of' acts as a link.
(Other definitions for gas that I've seen before include "chew the fat" , "natural resource" , "Oxygen maybe" , "Something exciting" , "Substance like air" .)