Work encountered back in time (5)
I believe the answer is:
tempo
'time' is the definition.
(tempo is a kind of time)
'work encountered back' is the wordplay.
'work' becomes 'op' (common abbreviation for 'opus').
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'back' shows that the letters should be reversed in order.
'op'+'met'='opmet'
'opmet' written backwards gives 'TEMPO'.
'in' acts as a link.
(Other definitions for tempo that I've seen before include "Cadence" , "Muscial time" , "Pace, rate" , "Metronome output" , "Speed or beat, musically" .)