Protect, secure (6)
I believe the answer is:
defend
I believe this is a double definition.
'protect' is the first definition.
(I know that defend is a type of protect)
'secure' is the second definition.
(thesaurus)
(Other definitions for defend that I've seen before include "Protect against challenge or attack" , "Act as a guard" , "Protect - guard" , "Resist an attack" , "Compete to retain (sporting title)" .)