The most common and most likely answer to this crossword clue is the 9 letter word HOLDOVERS
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Buddy explains!

The straight part
We know that "relics" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case relics = holdovers.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 HOLDOVERS mean?
HOLDOVERS noun- Something left behind, saved or remaining from an earlier time.
- The distance (at target) by which a rifle scope is aimed higher than the intended point of impact in order to compensate for bullet drop over the distance to the target.