The hour to go back from the Mitchell Pass (4)
I believe the answer is:
time
'the hour' is the definition.
(I've seen this in another clue)
'go back from the mitchell pass' is the wordplay.
'go back' shows that the letters should be reversed in order.
'from' indicates a hidden word.
'emit' is hidden within 'the mitchell pass'.
'emit' backwards is 'TIME'.
'to' acts as a link.
(Other definitions for time that I've seen before include "it may be Central European" , "See 12" , "Continuum of past, present and future" , "Prison sentence (colloq.)" , "The father of Truth, presumably" .)