Stony impression of one stuck in the past? (6)

I believe the answer is:

fossil

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'stony impression' is the definition.
'fossil' can be an answer for 'impression' (I have seen 'Lasting impression' mean 'fossil' so perhaps 'impression' could also mean 'fossil'). I am unsure of the 'stony' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for fossil that I've seen before include "Ancient remains embedded in rock" , "Animal remnant preserved in rock" , "Prehistoric relic" , "Fuddy-duddy" , "Petrified remains of plant or animal" .)

I've seen this clue in The Irish Times.

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