Aims of American agents to protect Republican... (7)
I believe the answer is:
aspires
'aims' is the definition.
('aspire' can be a synonym of 'aim')
'american agents to protect republican' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'agents' becomes 'spies' (spy is a kind of agent).
'to protect' is an insertion indicator.
'republican' becomes 'r' (abbreviation).
'spies' enclosing 'r' is 'spires'.
'a'+'spires'='ASPIRES'
'of' is the link.
(Other definitions for aspires that I've seen before include "Has ambition to" , "Has an ambitious plan" , "dreams" , "Hopes" , "Aims to rise" .)