It's held until a condition is fulfilled (6)
I believe the answer is:
escrow
'it's held until a condition is fulfilled' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for escrow that I've seen before include "fund held in trust?" , "It's held in trust or as a security" , "Money held against completion" , "Deed held by third party effective when a condition is met" , "goods held by third party" .)