Day starts with moderately soft rain. (4)
I believe the answer is:
damp
'rain' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'day starts with moderately soft' is the wordplay.
'starts' means to remove the last letter.
'with' says to put letters next to each other.
'moderately soft' becomes 'mp' (I can't explain this - if you can you should believe this answer much more).
'day' with its last letter taken off is 'da'.
'da'+'mp'='DAMP'
Can you help me to learn more?
(Other definitions for damp that I've seen before include "Somewhat moist" , "Rising -, TV sitcom" , "soggy" , "(Slightly) wet" , "Slightly moist" .)