Bent cops refine superintendent's case (9)
I believe the answer is:
dishonest
'bent' is the definition.
(bent can mean corrupt)
'cops refine superintendent's case' is the wordplay.
'cops' becomes 'DIs' (detective inspectors).
'refine' becomes 'hone' (hone can mean to refine or improve).
'case' means to remove the middle letters.
'superintendent' with its middle removed is 'st'.
'dis'+'hone'+'st'='DISHONEST'
(Other definitions for dishonest that I've seen before include "cheat" , "Corrupt" , "Not straightforward" , "Untruthful - mendacious" , "Not true!" .)