Crossword Genius

Ill-natured American police department (4)

Ross

I believe the answer is:

acid

'ill-natured' is the definition.

'american police department' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'police department' becomes 'cid' (I've seen this in other clues).
'a'+'cid'='ACID'

(Other definitions for acid that I've seen before include "So-called drug" , "Alkali's opposite" , "Drug LSD (colloq.)" , "Bitter or sour" , "Vinegary" .)

I've seen this clue in The Independent.
Want a hint initially instead of a full solution? Install my app