Submitted before the Spanish guard (8)
I believe the answer is:
sentinel
'guard' is the definition.
(sentinel is a kind of guard)
'submitted before the spanish' is the wordplay.
'submitted' becomes 'sentin' (I've seen this before).
'before' means one lot of letters go next to another.
'the spanish' becomes 'el'.
'sentin'+'el'='SENTINEL'
(Other definitions for sentinel that I've seen before include "Soldier who stands and keeps watch" , "One stands and keeps watch" , "One watches" , "Watching guard" , "Guard who stands and keeps watch" .)