Fool around like ingenues initially, in semi-darkness (6)
I believe the answer is:
twilit
'semi-darkness' is the definition.
(I've seen this before)
'fool around like ingenues initially' is the wordplay.
'fool' becomes 'twit' (both can mean a stupid person).
'around' is an insertion indicator.
'initially' suggests taking the first letters.
The initial letters of 'like ingenues' is 'li'.
'twit' going around 'li' is 'TWILIT'.
'in' is the link.
(Other definitions for twilit that I've seen before include "Not being fully illuminated" , "in the dusk" , "Dimly illuminated" , "Road surfacing" , "Somewhat dim" .)