In France, he's swallowed by lake of purplish hue (5)
I believe the answer is:
lilac
'hue' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for lilac that I've seen before include "Shrub (but not always this colour)" , "Lavender-coloured" , "Fragrant,purple flower" , "Pale violet hue" , "Genus Syringa shrub" .)