Accordingly, protecting against a grand capital city (8)
I believe the answer is:
santiago
'capital city' is the definition.
(Santiago is the capital of Chile)
'accordingly protecting against a grand' is the wordplay.
'accordingly' becomes 'so' (synonyms).
'protecting' indicates putting letters inside (inserted letters are held or protected).
'against' becomes 'anti' (prefix meaning against).
'grand' becomes 'g' (G is short for grand as in a thousand).
'anti'+'a'+'g'='antiag'
'so' enclosing 'antiag' is 'SANTIAGO'.
(Other definitions for santiago that I've seen before include "Capital of Chile" , "South American capital" , "Chile's capital" , "Chilean capital" , "City" .)