Substantial list includes North American soldier (8)
I believe the answer is:
tangible
'substantial' is the definition.
('tangible' can be a synonym of 'substantial')
'list includes north american soldier' is the wordplay.
'list' becomes 'table' (I've seen this before).
'includes' indicates putting letters inside.
'north' becomes 'n' ('N' can be a synonym of 'north').
'american soldier' becomes 'gi'.
'n'+'gi'='ngi'
'table' placed around 'ngi' is 'TANGIBLE'.
(Other definitions for tangible that I've seen before include "Actual" , "Material" , "Real and substantial" , "Touchable, real" , "Bleating in clear and definite manner" .)