Remains to be seen? (4)
'remains to be seen?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ruin that I've seen before include "Destroy completely" , "Wreck" , "Physical collapse" , "Wrecked building" , "Destory or bankrupt" .)
(Other definitions for ash that I've seen before include "Silvery-grey" , "What's often left after something 1 Ac" , "Runic letter; tree" , "Fraxinus" , "Grey-barked tree" .)