Protocol later allows outside security (10)
I believe the answer is:
collateral
'security' is the definition.
(collateral is a kind of security)
'protocol later allows outside' is the wordplay.
'outside' says the answer is hidden in the clue (a word is around or outside the answer).
'COLLATERAL' is hidden in the letters of 'protocol later allows'.
(Other definitions for collateral that I've seen before include "running side by side" , "subsidiary" , "Secondary; parallel" , "Guarantee" , "damage?" .)