Police force raised detective's rates (5)
I believe the answer is:
tempi
'rates' is the definition.
(tempo is a kind of rate)
'police force raised detective's' is the wordplay.
'police force' becomes 'met' (short for Metropolitan Police Service).
'raised' says the letters should be written in reverse (going up in a down clue).
'detective' becomes 'pi' (private eye).
'met' reversed gives 'tem'.
'tem'+'pi'='TEMPI'
(Other definitions for tempi that I've seen before include "Times" , "Speeds, rhythms of musical pieces" , "Rates" , "Speeds (music)" , "Beats" .)