Not initially enlightened but in the dark (5)
I believe the answer is:
unlit
'in the dark' is the definition.
(I've seen this in another clue)
'not initially enlightened' is the wordplay.
'not' becomes 'un' (prefix meaning 'not').
'initially' is a charade indicator (letters next to each other) (some letters go before others).
'enlightened' becomes 'lit' (I've seen this before).
'un'+'lit'='UNLIT'
'but' acts as a link.
(Other definitions for unlit that I've seen before include "Left in the dark" , "Not illuminated" , "Without illumination" , "not switched on" , "not exactly bright" .)