A god visiting America writes (7)
I believe the answer is:
authors
'writes' is the definition.
(authoring is a kind of writing)
'a god visiting america' is the wordplay.
'god' becomes 'thor' (Thor is an example**).
'visiting' means one lot of letters goes inside another.
'america' becomes 'us' (abbreviation for the United States).
'thor' going within 'us' is 'uthors'.
'a'+'uthors'='AUTHORS'
(Other definitions for authors that I've seen before include "Pens" , "Writers, generators" , "People who write" , "Writes" , "Writers, sources" .)