The compiler had substance and character (8)
I believe the answer is:
identity
'character' is the definition.
(I've seen this before)
'the compiler had substance' is the wordplay.
'the compiler' becomes 'i' (the person who is writing these clues).
'had' becomes 'd' (I've seen this in other clues).
'substance' becomes 'entity'.
'i'+'d'+'entity'='IDENTITY'
'and' acts as a link.
(Other definitions for identity that I've seen before include "One's sometimes mistaken" , "Sameness - individuality" , "sort of card" , "Distinct personality of an individual" , "It's on the cards" .)