Friend right; I have almost all the substance (8)
I believe the answer is:
material
'substance' is the definition.
(I know that substance can be written as material)
'friend right i have almost all' is the wordplay.
'friend' becomes 'mate' (mate is a kind of friend).
'right' becomes 'r' (common abbreviation).
'have' is a charade indicator (letters next to each other).
'almost' means to remove the last letter (most of the word but not all of it).
'all' with its last letter taken away is 'al'.
'mate'+'r'+'i'+'al'='MATERIAL'
'the' acts as a link.
(Other definitions for material that I've seen before include "Important; fabric" , "it is of some significance" , "Fabric, stuff" , "Felt, perhaps" , "Matter; cloth" .)