Series of tests to perform check (4)
I believe the answer is:
stop
'check' is the definition.
(I know that check is a kind of stop)
'series of tests to perform' is the wordplay.
'series of' says the answer is hidden in the clue (a series of letters from the clue).
'STOP' is hidden within 'tests to perform'.
(Other definitions for stop that I've seen before include "Plug; cease" , "Halt, whoa, desist" , "Pack it in - bar" , "Standstill" , "oboe, perhaps" .)