Time to be part of system, possibly (5)
I believe the answer is:
tempo
'time' is the definition.
(tempo is a kind of time)
'part of system possibly' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'TEMPO' can be found hidden inside 'system possibly'.
'to be' acts as a link.
(Other definitions for tempo that I've seen before include "Speed of 3A" , "(Musically) the speed to be played" , "Pace of a musical piece" , "Pace of a piece of music" , "Beat (music)" .)