A northern wood said to be of great age (7)
I believe the answer is:
antique
'be of great age' is the definition.
(I've seen this before)
'a northern wood said' is the wordplay.
I cannot quite understand how this works, but
'a' could be 'an' and 'an' is found within the answer.
'said' could be 't' (I've seen this in other clues) and 't' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
(Other definitions for antique that I've seen before include "Archaic" , "Valuable due to age, like some furniture" , "Object valued because of age" , "from long ago" , "(Something) valuable because of age and quality" .)