Sun set to the west - how disappointing (4)
I believe the answer is:
rats
'sun set to the west how disappointing' is the definition.
I can't judge whether this definition defines the answer.
'sun set to the' is the wordplay.
'sun' becomes 'Ra' (ancient Egyptian sun god).
'set' becomes 's' (I can't explain this - if you can you should give a lot more credence to this answer).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
's' after 't' is 'ts'.
'ra'+'ts'='RATS'
Can you help me to learn more?
(Other definitions for rats that I've seen before include "Heels" , "Curse" , "Rodent pests" , "Snoopy's imprecation - vermin" , "Mild oath - sewer residents" .)