Crosby piece played by youngsters (4)
I believe the answer is:
boys
'played by youngsters' is the definition.
The answer and definition can be both people as well as being plural nouns.
Perhaps you can see an association between them that I can't see?
'crosby piece' is the wordplay.
I cannot really understand how this works, but
'piece' could be 'b' (abbreviation for bishop) and 'b' is found within the answer.
The remaining letters 'oys' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for boys that I've seen before include "Young males" , "Male children" , "Lads" , "Young men" , "Beach --, group" .)