The most common and most likely answer to this crossword clue is the 5 letter word POCKY
P
O
C
K
Y
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The straight part
We know that "Damned old" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case damned old = pocky.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 POCKY mean?
POCKY adjective- Covered in pock marks; specifically, pox-ridden, syphilitic.