Prove wrong potato perhaps has been sent back (5)
I believe the answer is:
rebut
'prove wrong' is the definition.
(I've seen this before)
'potato perhaps has been sent back' is the wordplay.
'potato perhaps' becomes 'tuber' (potato is an example of a tuber).
'has been sent back' says the letters should be written in reverse.
'tuber' in reverse letter order is 'REBUT'.
(Other definitions for rebut that I've seen before include "Deny claim" , "Brute can refute" , "Tuber (anag.)" , "Drive back" , "Overturn" .)