Thus good is enshrined in lead character, though not at first (4)
I believe the answer is:
ergo
'thus' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ergo that I've seen before include "It follows" , "'Cogito, ---- sum'" , "'Therefore, to the old Romans (4)'" , "so philosopher wrote in Latin" , "Thus" .)