One article is about a desert (5)
I believe the answer is:
sinai
'a desert' is the definition.
(I know that Sinai is a desert)
'one article is about' is the wordplay.
'one' becomes 'i' (Roman numeral).
'article' becomes 'an' (English indefinite article).
'about' is a reversal indicator.
'i'+'an'+'is'='ianis'
'ianis' written backwards gives 'SINAI'.
(Other definitions for sinai that I've seen before include "Mountain in Egypt" , "One showing genetic change" , "Ten Commandments mountain" , "Mt. where Moses received 10 Commandments" , "11 Across peninsula" .)