The most common and most likely answer to this crossword clue is the 9 letter word NEOLITHIC
I've seen this crossword clue in The Times
N
E
O
L
I
T
H
I
C
More clues leading to the result NEOLITHIC
- Old age impaired one settled here in Rome
- Mostly gas-fired, this Latin period
- In Chile, to recreate Stone Age
- Age-old ethnic conflict over crude oil
- Period at sea once, with books welcome on board
- Born ordinary, left India mostly stupid, as from the Stone Age
- Break into Chile, just like the old days?
- 9 Going out to Chile in old age
- From a bygone age, nasty one fired bumpkin slightly lacking
Buddy explains!

The straight part
We know that "Old age" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old age = neolithic.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does NEOLITHIC mean?
NEOLITHIC adjective- Hopelessly outdated