Cryptic crossword clue
Ill health’s so sad, invalid being extremely ancient 2,3,2,3,5

The most common and most likely answer to this crossword clue is the 2 plus 3 plus 2 plus 3 plus 5 letter word AS OLD AS THE HILLS

I've seen this crossword clue in The Daily Telegraph
A
S
O
L
D
A
S
T
H
E
H
I
L
L
S

Buddy explains!

The straight part
We know that "extremely ancient" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extremely ancient = as old as the hills.
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.

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