Woody could be American, attached to foreign legion (8)
I believe the answer is:
ligneous
'woody' is the definition.
('ligneous' can be similar in meaning to 'woody')
'american attached to foreign legion' is the wordplay.
'american' becomes 'us'.
'attached to' says to put letters next to each other.
'foreign' is an anagram indicator (foreign order of the letters).
'legion' is an anagram of 'ligneo'.
'us' after 'ligneo' is 'LIGNEOUS'.
'could be' is the link.
(Other definitions for ligneous that I've seen before include "Wooden" , "Woody" , "Of the nature of wood" , "Made of wood" .)