Preoccupation (9)
I believe the answer is:
obsession
'preoccupation' is the definition.
(I know that obsession is a type of preoccupation)
This is all the clue.
(Other definitions for obsession that I've seen before include "Phobia" , "Fixed idea" , "Persistent preoccupation" , "Enthusiasm" , "Unhealthy compulsion" .)