A curtness needing correction in old people (9)
I believe the answer is:
etruscans
'old people' is the definition.
(ancient civilization)
'a curtness needing correction in' is the wordplay.
'needing correction' is an anagram indicator (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'curtness' is an anagram of 'etruscns'.
'a' placed within 'etruscns' is 'ETRUSCANS'.
(Other definitions for etruscans that I've seen before include "Ancient Italians" , "Old Italians" , "old people in Italy" .)