Ancient gallows, possibly oak (4)

I believe the answer is:

tree

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This clue could be a double definition.

'ancient gallows' is the first definition.
'tree' can be an answer for 'gallows' (I've seen this in another clue). I am unsure of the 'ancient' bit.

'oak' is the second definition.
(I've seen this before)

'possibly' acts as a link.

Can you help me to learn more?

(Other definitions for tree that I've seen before include "- Frog; - house" , "Plant with trunk (which families have)" , "Tall, woody plant" , "Box or bay maybe?" , "Genealogist's graphic" .)

I've seen this clue in the Evening Standard.

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