Quickly eat sandwich with zero filling .. (4)
I believe the answer is:
bolt
'quickly eat' is the definition.
'bolt' can be an answer for 'eat' (bolting is a kind of eating). I am not sure about the 'quickly' bit.
'sandwich with zero filling' is the wordplay.
'sandwich' becomes 'BLT' (BLT is an example).
'with zero' becomes 'o' (O resembles 0. I am not sure about the 'with' bit.).
'filling' indicates putting letters inside.
'blt' going around 'o' is 'BOLT'.
Can you help me to learn more?
(Other definitions for bolt that I've seen before include "writer" , "Escape" , "Short arrow for a crossbow" , "Run away suddenly; long fixing pin" , "A . . . . from the blue is a complete surprise" .)