I'm going to light up Shakespearean setting (7)
I believe the answer is:
illyria
'shakespearean setting' is the definition.
(I've seen this before)
'i'm going to light up' is the wordplay.
'i'm going to' becomes 'I'll' ('I'm going to' can mean 'I will' or 'I'll').
'light' becomes 'airy' (synonyms).
'up' is a reversal indicator (in down clue: letters go upwards).
'airy' reversed gives 'yria'.
'ill'+'yria'='ILLYRIA'
(Other definitions for illyria that I've seen before include "Classical Albania" , "Orsino's place" , "Orsino's dukedom" , "Ancient region of Adriatic coast, setting for Twelfth Night" , "setting at start of Twelfth Night" .)