City of Gold secure against nothing (7)
I believe the answer is:
orlando
'city' is the definition.
(I've seen this before)
'gold secure against nothing' is the wordplay.
'gold' becomes 'or' ('or' is the heraldic name for gold).
'secure' becomes 'land' (land can mean to secure or obtain).
'against' means one lot of letters go next to another.
'nothing' becomes 'O' (looks like zero - 0).
'or'+'land'+'o'='ORLANDO'
'of' is the link.
(Other definitions for orlando that I've seen before include "American themepark location" , "Romantic lead in "As You Like It" - the Marmalade Cat" , "Floridian city of Disney World" , "Florida location" , "place in Florida" .)