Charm offensive ultimately linked to war associated with us (7)
I believe the answer is:
enamour
'charm' is the definition.
(synonyms)
'offensive ultimately linked to war associated with us' is the wordplay.
'ultimately' suggests the final letters.
'linked to' says to put letters next to each other.
'war' becomes 'nam' (informal term for the Vietnam War).
'associated with us' becomes 'our' ('our' is the possessive pronoun for 'us').
The last letter of 'offensive' is 'e'.
'e'+'nam'+'our'='ENAMOUR'
(Other definitions for enamour that I've seen before include "entrance" , "Delight" , "Our name (anag)" , "Enchant" , "Charm, captivate" .)