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 definition defines the answer.
'bone found in barrow' is the wordplay.
'bone' becomes 'rib' (rib is a type of bone).
'found in' indicates putting letters inside.
'barrow' becomes 'mound' (I can't explain this - if you can you should give a lot more credence to this answer).
'rib' going into '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" .)