Argentine novel about old age (10)
I believe the answer is:
generation
'age' is the definition.
(thesaurus)
'argentine novel about old' is the wordplay.
'novel' indicates an anagram.
'about' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'argentine' with letters rearranged gives 'generatin'.
'generatin' enclosing 'o' is 'GENERATION'.
(Other definitions for generation that I've seen before include "About thirty years'" , "group of similar age" , "young" , "what was lost in WW1" , "Everyone of same age" .)