Preoccupied and shaken, lacking time to overcome brain disease (8)
I believe the answer is:
obsessed
'preoccupied' is the definition.
(I know that preoccupied can be written as obsessed)
'shaken lacking time to overcome brain disease' is the wordplay.
I cannot quite understand how this works, but
'disease' could be 'bse' (bovine spongiform encephalopathy, mad cow disease) and 'bse' is found within the answer.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Other definitions for obsessed that I've seen before include "With compulsion" , "With mind continually occupied, abnormally focused" , "Excessively preoccupied" , "Fanatical" , "Persistently preoccupied" .)