Looking embarrassed about the sad ending (3)
I believe the answer is:
red
'looking embarrassed' is the definition.
(I've seen this before)
'about the sad ending' is the wordplay.
'about' becomes 're' (common abbreviation for 'with reference to').
'ending' says to take the final letters.
The last letter of 'sad' is 'd'.
're'+'d'='RED'
(Other definitions for red that I've seen before include "Stop light" , "Very angry, seeing this" , "Colour of blood" , "Inflamed" , "A colourful communist" .)