Talk to WI about power unit (8)
I believe the answer is:
kilowatt
'power unit' is the definition.
(kilowatt is a kind of power unit)
'talk to wi about' is the wordplay.
'about' indicates an anagram.
'talk'+'to'+'wi'='talktowi'
'talktowi' with letters rearranged gives 'KILOWATT'.
(Other definitions for kilowatt that I've seen before include "Unit of energy" , "Unit of electric power" , "One thousand joules per second" , "kW" , "Unit of electrical power" .)