Stake required, unlimited (4)
I believe the answer is:
ante
'stake' is the definition.
(anteing is a kind of staking)
'required unlimited' is the wordplay.
'required' becomes 'wanted' ('want' can be a synonym of 'require').
'unlimited' says to take the centre (discard the edges or 'limits' of the word).
The central letters of 'wanted' are 'ANTE'.
(Other definitions for ante that I've seen before include "Money for poker" , "Initial stake in a poker game" , "Betting stake" , "Preposition meaning before" , "Stake (that may be upped?)" .)