Clue: Feature of corner about to disappear, making light of caution (5)
Answer: AMBER
Explanation: Definition: light of caution

(c)**AMBER** ("feature of corner") with C (circa, so "about") *disappearing*
 
*I don't think "camber" and "feature of corner" are synonymous – a camber is a curve, which to me is the antithesis of a corner, which would be sharp.