Asleep, Carol is interrupted by awful rumble (10)
I believe the answer is:
slumbering
'asleep' is the definition.
('slumbering' can be similar in meaning to 'asleep')
'carol is interrupted by awful rumble' is the wordplay.
'carol' becomes 'sing' (I've seen this in other clues).
'is interrupted by' indicates putting letters inside.
'awful' indicates an anagram.
'rumble' with letters rearranged gives 'lumber'.
'sing' placed around 'lumber' is 'SLUMBERING'.
(Other definitions for slumbering that I've seen before include "asleep" , "napping" , "lying dormant?" , "sleeping" .)