Black rodent finds horrible kid (4)
I believe the answer is:
brat
'horrible kid' is the definition.
'brat' can be an answer for 'kid' (brat is a kind of kid). I am not certain of the 'horrible' bit.
'black rodent' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'rodent' becomes 'rat' (rat is a kind of rodent).
'b'+'rat'='BRAT'
'finds' acts as a link.
Can you help me to learn more?
(Other definitions for brat that I've seen before include "A spoiled badly-behaved child" , "Little terror" , "Ill-behaved child" , "annoying young fellow" , "An obnoxious or spoiled child" .)