Issue as the hour goes back (4)
I believe the answer is:
emit
'issue' is the definition.
(both can mean to give out or radiate)
'the hour goes back' is the wordplay.
'the hour' becomes 'time' (I've seen this in another clue).
'goes back' says the letters should be written in reverse.
'time' back-to-front is 'EMIT'.
'as' acts as a link.
(Other definitions for emit that I've seen before include "Broadcast" , "Send out in time" , "Exhale" , "Produce and discharge" , "Give off or discharge" .)