Mischievous child, one using cane on swimmer? (14)
I believe the answer is:
whippersnapper
'mischievous child' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'one using cane on swimmer?' is the wordplay.
'one using cane on' becomes 'whipper' (I can't justify this - if you can you should believe this answer much more).
'swimmer?' becomes 'snapper' (snapper is a kind of fish).
'whipper'+'snapper'='WHIPPERSNAPPER'
Can you help me to learn more?
(Other definitions for whippersnapper that I've seen before include "Impudent lad" , "cheeky young lad" , "Nonentity" , "cheeky upstart" , "Jumped-up youngster" .)