Crumbling bone found in barrow (8)

I believe the answer is:
moribund
'crumbling bone found in barrow' is the definition.
I can't tell whether this defines the answer.
'bone found in barrow' is the wordplay.
'bone' becomes 'rib' (rib is a type of bone).
'found in' means one lot of letters goes inside another.
'barrow' becomes 'mound' (I can't explain this - if you can you should believe this answer much more).
'rib' going inside 'mound' is 'MORIBUND'.
Can you help me to learn more?
(Other definitions for moribund that I've seen before include "Near to death" , "on the way out" , "In a dying state" , "Not growing or changing" , "At the point of death" .)
