Quick to get a bit redder in the sun (6)
I believe the answer is:
sudden
'quick' is the definition.
(similar in meaning)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sudden that I've seen before include "Occurring unexpectedly quickly" , "Unexpected, without warning" , "Done unexpectedly" , "Rapid and unexpected" , "Abrupt, unexpected" .)