Key of Galaxy? (5,3)
I believe the answer is:
space bar
This clue could be a double definition.
'key' is the first definition.
(space bar is a kind of key)
'galaxy?' is the second definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for space bar that I've seen before include "Keyboard key" , "Longest typing key" , "used by typists?" , "Key feature" , "key, large one" .)