Work fulfilled? About time (5)
I believe the answer is:
tempo
'time' is the definition.
(tempo is a kind of time)
'work fulfilled? about' is the wordplay.
'work' becomes 'op' (common abbreviation for 'opus').
'fulfilled?' becomes 'met' (fulfilling is a kind of meeting).
'about' shows that the letters should be reversed in order.
'op'+'met'='opmet'
'opmet' backwards is 'TEMPO'.
(Other definitions for tempo that I've seen before include "Musical time" , "Speed of a musical piece" , "Musical beat or rhythm" , "(Musically) the speed to be played" , "Pace - pacing" .)