Hold off the Spanish invading Gulf (5)
I believe the answer is:
belay
'hold off' is the definition.
'belay' can be an answer for 'hold' (thesaurus). I'm not sure about the 'off' bit.
'the spanish invading gulf' is the wordplay.
'the spanish' becomes 'la' ('the' in Spanish).
'invading' indicates putting letters inside.
'gulf' becomes 'bey' (I can't justify this - if you can you should give a lot more credence to this answer).
'la' going inside 'bey' is 'BELAY'.
Can you help me to learn more?
(Other definitions for belay that I've seen before include "Make fast" , "Stop" , "Turn a rope round something to secure it" .)