Sir Galahad ditches rags unexpectedly in favour of brightly coloured flower (6)
I believe the answer is:
dahlia
'favour of brightly coloured flower' is the definition.
'dahlia' can be an answer for 'flower' (dahlia is a kind of flower). I'm unsure of the 'favour of brightly coloured' bit.
'sir galahad ditches rags unexpectedly' is the wordplay.
'ditches' indicates named letters should be taken away.
'unexpectedly' indicates an anagram.
'sir'+'galahad'='sirgalahad'
'sirgalahad' with 'rags' removed is 'ilahad'.
'ilahad' with letters rearranged gives 'DAHLIA'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for dahlia that I've seen before include "Flower genus" , "Flower named after a Swedish botanist, d. 1789" , "Showy garden flower" , "Showy garden plant" , "Showy flower from Mexico" .)