The colour of the saucer is emerald (6)
I believe the answer is:
cerise
'the colour' is the definition.
(cerise is a kind of colour)
'of the saucer is emerald' is the wordplay.
'of' indicates the answer is hidden within the clue.
'CERISE' is hidden within 'saucer is emerald'.
(Other definitions for cerise that I've seen before include "Light red colour" , "Cherry red colour" , "Bright cherry-red colour" , "Pinkish red" , "Vivid reddish-pink" .)