Sound made to attract attention by some cops sternly (4)
I believe the answer is:
psst
'sound made to attract attention' is the definition.
I can't judge whether this definition defines the answer.
'some cops sternly' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'PSST' is hidden within 'cops sternly'.
'by' acts as a link.
Can you help me to learn more?
(Other definitions for psst that I've seen before include "Call to attract attention" , "Sibilant sound made to attract attention" , "Beckoning sound" , "Don't tell anyone" , "Here's a secret" .)