Centre upset some owner-occupiers (4)
I believe the answer is:
core
'centre' is the definition.
(core can mean something's centre)
'upset some owner-occupiers' is the wordplay.
'upset' says the letters should be written backwards.
'some' says the answer is hidden in the clue (some parts of the word are used).
'eroc' is hidden in the letters of 'owner occupiers'.
'eroc' in reverse letter order is 'CORE'.
(Other definitions for core that I've seen before include "Kernel" , "essential element" , "Planet's centre" , "Central part of an apple" , "Central zone" .)