Vast expanse of promotional work that is full of attitude (7)
I believe the answer is:
prairie
'vast expanse' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'promotional work that is full of attitude' is the wordplay.
'promotional work' becomes 'PR' (public relations).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'full of' means one lot of letters goes inside another.
'attitude' becomes 'air' (I've seen this before).
'pr'+'ie'='prie'
'prie' enclosing 'air' is 'PRAIRIE'.
'of' is the link.
Can you help me to learn more?
(Other definitions for prairie that I've seen before include "North American grassland" , "Open grassland in the USA" , "Schooners once crossed it" , "Grasslands" , "American plain" .)