Subject matter to cover in huge area (9)
I believe the answer is:
continent
'huge area' is the definition.
The definition and answer can be both locations as well as being singular nouns.
Maybe there's an association between them I don't understand?
'subject matter to cover in' is the wordplay.
'subject matter' becomes 'content' (synonyms).
'to cover' is an insertion indicator.
'content' going around 'in' is 'CONTINENT'.
Can you help me to learn more?
(Other definitions for continent that I've seen before include "Africa, say" , "dry?" , "Temperate - land mass" , "Virtuous" , "Large land mass - exercising self-restraint" .)