She appears in an ensemble that's rather colourless (5)
I believe the answer is:
ashen
'colourless' is the definition.
(similar in meaning)
'she appears in an' is the wordplay.
'appears in' means one lot of letters goes inside another.
'she' placed inside 'an' is 'ASHEN'.
'ensemble that's rather' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for ashen that I've seen before include "Anaemic-looking" , "Having gone pale" , "'Very pale, from shock say (5)'" , "Anaemic looking" , "Drained of colour" .)