English police in charge? That's sickening (6)
I believe the answer is:
emetic
'sickening' is the definition.
(I've seen this before)
'english police in charge?' is the wordplay.
'english' becomes 'e' (abbreviation).
'police' becomes 'met' (London Metropolitan Police).
'in charge?' becomes 'ic' (abbreviation for 'in charge').
'e'+'met'+'ic'='EMETIC'
'that's' acts as a link.
(Other definitions for emetic that I've seen before include "Medicine to make someone throw up" , "Medicine taken to induce vomiting" , "Medicine taken to make one vomit" , "Ipecacuanha is one" , "making you throw up" .)