Microwave setting (6)
I believe the answer is:
reheat
'microwave setting' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for reheat that I've seen before include "Jet engine afterburner" , "Process increasing jet engine thrust" , "Warm (food) up again" , "Bring back to the boil, for instance" , "Cook again" .)