Joker returns in the flesh, initially tasting a lot of power (8)
I believe the answer is:
megawatt
'a lot of power' is the definition.
I can't tell whether this definition defines the answer.
'joker returns in the flesh initially tasting' is the wordplay.
'joker' becomes 'wag' (I've seen this before).
'returns' says the letters should be written in reverse.
'in the' indicates putting letters inside.
'flesh' becomes 'meat' (flesh is meat).
'initially' indicates taking the first letters.
The first letter of 'tasting' is 't'.
'wag' reversed gives 'gaw'.
'gaw' going inside 'meat' is 'megawat'.
'megawat'+'t'='MEGAWATT'
Can you help me to learn more?
(Other definitions for megawatt that I've seen before include "Unit of electrical power" , "measure of power" .)