Rate of workforce's retirement? (5)

I believe the answer is:

tempo

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'rate' is the definition.
(tempo is a kind of rate)

I cannot understand how the remainder of the clue works.

(Other definitions for tempo that I've seen before include "Rhythm of piece of music" , "Beat (music)" , "Rate and rhythm in music" , "Speed at which piece of music is played" , "Musical time" .)

I've seen this clue in The Independent.

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