Short-term workers receiving ordinary rates (6)
I believe the answer is:
tempos
'rates' is the definition.
'short-term workers receiving ordinary' is the wordplay.
'short-term workers' becomes 'temps'.
'receiving' is an insertion indicator.
'ordinary' becomes 'o' (abbreviation e.g. O-Levels).
'temps' enclosing 'o' is 'TEMPOS'.
(Other definitions for tempos that I've seen before include "Speeds at which compositions are played" , "Times" , "Musical speeds" .)