Preoccupied (8)
'preoccupied' is the definition.
(I know that preoccupied can be written as obsessed)
This is the entire clue.
(Other definitions for obsessed that I've seen before include "Excessively preoccupied" , "Compulsively concerned with something" , "Fanatical" , "With compulsion" , "Showing excessive or compulsive concern with something" .)
'preoccupied' is the definition.
(synonyms)
This is all the clue.
(Other definitions for abstracted that I've seen before include "Removed - preoccupied - absent-minded" , "miles away" , "not paying attention" , "Summarised -- lacking concentration" , "without concentrating" .)