Some boy, a hooligan, undesirable (5)
I believe the answer is:
yahoo
'undesirable' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?
'some boy a hooligan' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'YAHOO' is hidden in the letters of 'boy a hooligan'.
Can you help me to learn more?
(Other definitions for yahoo that I've seen before include "Brute, lout" , "Swiftian ruffian" , "Uncouth person" , "Rude or coarse person" , "Brutish animal species from Gulliver's Travels" .)