Ruined, seeing miserable rounding error (9)
I believe the answer is:
collapsed
'ruined' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'miserable rounding error' is the wordplay.
I cannot really understand how this works, but
'error' could be 'lapse' (lapse is a kind of error) and 'lapse' is present in the answer.
The remaining letters 'cold' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'seeing' is the link.
Can you help me to learn more?
(Other definitions for collapsed that I've seen before include "Gave way, caved in" , "Cracked up - gave way" , "laid low" , "Fell apart" .)