Very quick power nap, perhaps, then nothing (6)
I believe the answer is:
presto
'very quick' is the definition.
'power nap perhaps then nothing' is the wordplay.
'power' becomes 'p' (symbol in physics).
'nap perhaps' becomes 'rest' (I've seen this in another clue. I am not sure about the 'perhaps' bit.).
'then' is a charade indicator (letters next to each other).
'nothing' becomes 'O' (looks like zero - 0).
'p'+'rest'+'o'='PRESTO'
Can you help me to learn more?
(Other definitions for presto that I've seen before include "Hey, it's a magician's word" , "Hey, quickly for a magician" , "fast to the maximum" , "scored quickly" , "Poster (anag.)" .)