Cool flower, grand, Claire arranged (7)
I believe the answer is:
glacier
'cool flower' is the definition.
'glacier' can be an answer for 'flower' (I have seen 'River of ice' mean 'glacier' so perhaps 'river' could also mean 'glacier'). I am not sure about the 'cool' bit.
'grand claire arranged' is the wordplay.
'grand' becomes 'g' (G is short for grand as in a thousand).
'arranged' indicates anagramming the letters.
'claire' anagrammed gives 'lacier'.
'g'+'lacier'='GLACIER'
Can you help me to learn more?
(Other definitions for glacier that I've seen before include "Slowly moving mass of ice" , "Creeping ice mass" , "Mass of ice moving down a mountain" , "Slow-moving mass of ice" , "Large flow of ice" .)