Work force turning back time (5)
I believe the answer is:
tempo
'time' is the definition.
(tempo is a kind of time)
'work force turning back' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'force' becomes 'met' (I've seen this in other clues).
'turning back' says the letters should be written in reverse.
'op'+'met'='opmet'
'opmet' reversed gives 'TEMPO'.
(Other definitions for tempo that I've seen before include "Muscial time" , "Cadence" , "Speed or beat, musically" , "Metronome output" , "Speed at which piece of music is played" .)