It's refreshing - nothing possibly to be sad about (4)
I believe the answer is:
soda
'it's refreshing' is the definition.
I can't judge whether this defines the answer.
'nothing possibly to be sad about' is the wordplay.
I cannot really understand how this works, but
'nothing' could be 'o' (O resembles 0) and 'o' is found in the answer.
an anagram of 'sad' is 'sda' which is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for soda that I've seen before include "Soft drink" , "Whisky mixer" , "Sodium carbonate" , "Alkaline substance used in cleaning, drinks etc" , "fizz" .)