Low blow has the cop in a bad way (5,4)
I believe the answer is:
cheap shot
'low blow' is the definition.
(I've seen this in another clue)
'has the cop in a bad way' is the wordplay.
'in a bad way' indicates anagramming the letters.
'has'+'the'+'cop'='hasthecop'
'hasthecop' with letters rearranged gives 'CHEAP SHOT'.
(Other definitions for cheap shot that I've seen before include "Unkind act" , "Barbed comment exploiting known weakness of target" .)