Australian bounder, a bit of a crook (3)
I believe the answer is:
roo
'australian bounder' is the definition.
'roo' can be an answer for 'bounder' (short for kangaroo, something which bounds). I am not sure about the 'australian' bit.
'a bit of a crook' is the wordplay.
'a bit of' indicates the answer is hidden within the clue.
'ROO' is hidden within 'crook'.
Can you help me to learn more?
(Other definitions for roo that I've seen before include "companion of Pooh" , "Kangaroo (Austr. colloq.)" , "Hopper" , "Aussie jumper!" , "Young marsupial" .)