Be beaten by Leo's replacement (4)
I believe the answer is:
lose
'be beaten' is the definition.
(I've seen this before)
'leo's replacement' is the wordplay.
'replacement' is an anagram indicator.
'leos' with letters rearranged gives 'LOSE'.
'by' is the link.
(Other definitions for lose that I've seen before include "Suffer a defeat" , "Mislay - fail" , "Don't win" , "Fail to win" , "Shake off (a pursuer)" .)