Current tests pushed back repressive force (5)
I believe the answer is:
stasi
'repressive force' is the definition.
(secret police of East Germany)
'current tests pushed back' is the wordplay.
'current' becomes 'i' (symbol for electric current).
'tests' becomes 'sats' (exams taken in UK schools).
'pushed back' says the letters should be written in reverse.
'i'+'sats'='isats'
'isats' in reverse letter order is 'STASI'.
(Other definitions for stasi that I've seen before include "Force that spied" , "old secret service" , "East German Secret Police" , "Former German security service" , "Secret police of the former German Democratic Republic" .)