Sad, unlike Edith Piaf? (9)
I believe the answer is:
regretful
'sad' is the definition.
(similar in meaning)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for regretful that I've seen before include "Wishing something hadn't happened" , "Feeling remorse" , "Miss Otis was" , "Feeling sorry, repentant" , "but not Ms Piaf" .)