Submitted to the Spanish guard (8)
I believe the answer is:
sentinel
'guard' is the definition.
(I know that sentinel is a type of security guard)
'submitted to the spanish' is the wordplay.
'submitted' becomes 'sent in' (I've seen this before).
'to the spanish' becomes 'el' ('the' in Spanish).
'sentin'+'el'='SENTINEL'
(Other definitions for sentinel that I've seen before include "One stands and keeps watch" , "Watching guard" , "Look-out, military guard" , "Look out" , "Soldier keeping watch" .)