Thousand in cash for naughty youngster (6)
I believe the answer is:
monkey
This clue could be a double definition.
'thousand in cash' is the first definition.
(slang term for a thousand pounds)
'naughty youngster' is the second definition.
'monkey' can be an answer for 'youngster' (monkey is a kind of youngster). I am unsure of the 'naughty' bit.
'for' is the link.
Can you help me to learn more?
(Other definitions for monkey that I've seen before include "Mischievous type" , "Naughty child; primate" , "Chile pine (the Araucaria tree)" , "Any of various long-tailed primates" , "Mischievous child; primate" .)