Flog despicable person, pest seen down under (4,4)
I believe the answer is:
cane toad
'down under' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'flog despicable person pest' is the wordplay.
'flog' becomes 'cane' ('cane' can be a synonym of 'flog').
'despicable person pest' becomes 'toad' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'cane'+'toad'='CANE TOAD'
'seen' acts as a link.
Can you help me to learn more?
(Other definitions for cane toad that I've seen before include "Large amphibian pest in Australia" , "pest controller" .)