Stoppage in existence after store failing to close (6)
I believe the answer is:
stasis
'stoppage' is the definition.
(I've seen this before)
'in existence after store failing to close' is the wordplay.
'in existence' becomes 'is' (if something 'is', it exists).
'after' says to put letters next to each other.
'store' becomes 'stash' (stash is a kind of store).
'failing to close' means to remove the last letter (not having a closing letter).
'stash' with its final letter removed is 'stas'.
'is' after 'stas' is 'STASIS'.
(Other definitions for stasis that I've seen before include "Standstill" , "Cessation" , "Stoppage of blood circulation" , "State of immobility or inactivity" , "Assist in state of stagnation" .)