Checking the extremes on the deceptive operation (7)
I believe the answer is:
testing
'checking' is the definition.
('test' can be a synonym of 'check')
'the extremes on the deceptive operation' is the wordplay.
'extremes' means to remove the middle letters.
'on' says to put letters next to each other.
'the deceptive operation' becomes 'sting' (I've seen this in another clue).
'the' with its centre taken out is 'te'.
'te'+'sting'='TESTING'
(Other definitions for testing that I've seen before include "of a difficult nature" , "stressful" , "... conducting exam" , "Examining" , "Trying out" .)