Stake partly guaranteed (4)
I believe the answer is:
ante
'stake' is the definition.
(I've seen this before)
'partly guaranteed' is the wordplay.
'partly' indicates a hidden word.
'ANTE' can be found hidden inside 'guaranteed'.
(Other definitions for ante that I've seen before include "early payment" , "Betting stake" , "'Behind, before (4)'" , "Stake put up by a poker-player before receiving cards" , "not post" .)