8 across
Use
unknown
technique
for
out-of-this-world
23
(5,3)
Use unknown technique for out-of-this-world 23 (5,3)
hints
0
checks
0
hints
The definition is at the end of the clue.
How the clue works
Look at out-of-this-world 23 as the definition — 23 being a cross-reference to another clue whose answer is "galaxy", and the Milky Way is indeed our galaxy. For the wordplay, MILK gives you "use" (as in to exploit something), Y is your "unknown" (the algebraic variable), and WAY means "technique". String them together and there it is.