Quantity of coal you'd be thankful to have? (8)
I believe the answer is:
grateful
'quantity of coal' is the definition.
(I've seen this before)
'you'd be thankful to have?' is the wordplay.
I cannot quite see how this works, but
'be' could be 'rate' (rating is a kind of being) and 'rate' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for grateful that I've seen before include "Showing gratitude" , "quantity of coal" , "Thankful, appreciative" , "Felt a rug (anag)" , "Showing thankfulness" .)