Somewhat obscure half moon in the sky (5)
I believe the answer is:
smoky
'somewhat obscure' is the definition.
I can't judge whether this defines the answer.
'half moon in the sky' is the wordplay.
'half' indicates taking half.
'in the' is an insertion indicator.
'moon' with half the letters taken is 'mo'.
'mo' inserted within 'sky' is 'SMOKY'.
Can you help me to learn more?
(Other definitions for smoky that I've seen before include "Filled with tobacco fumes" , "Reeky" .)