Something in night sky seen in deserts to the west (4)
I believe the answer is:
star
'something in night sky' is the definition.
I know that 'night' relates to this answer.
'deserts to the west' is the wordplay.
'deserts' becomes 'rats' (abandons treacherously).
'to the west' says the letters should be written backwards (letters written right to left or 'east to west').
'rats' in reverse letter order is 'STAR'.
'seen in' acts as a link.
Can you help me to learn more?
(Other definitions for star that I've seen before include "Screen idol" , "Eg, Rigel, Aldebaran" , "Famous actor" , "Symbol of excellence" , "See 5" .)