Turn back (5)
'turn back' is the definition.
(I know that turn back can be written as reverse)
This is all the clue.
(Other definitions for reverse that I've seen before include "Britannia's place" , "Back (of a coin or medal)" , "come back" , "Turn inside out or upside down" , "Setback; go back" .)
(Other definitions for reset that I've seen before include "Put together again" , "question that's appeared in exam again" , "Restore to the initial readings" , "button on electronic device?" , "Turn back to zero" .)