Rescued, but unhappy about the great day (5)
I believe the answer is:
saved
'rescued' is the definition.
(similar in meaning)
'unhappy about the great day' is the wordplay.
'unhappy' becomes 'sad' (associated in meaning).
'about' is an insertion indicator.
'the great day' becomes 've' (I can't explain this - if you can you should believe this answer much more).
'sad' enclosing 've' is 'SAVED'.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for saved that I've seen before include "Put money by for a rainy day" , "Kept for later" , "Conserved" , "Stored for future use" , "Redeemed or rescued" .)