Center
'center' is the definition.
(synonyms)
This is all the clue.
(Other definitions for core that I've seen before include "Central part of an apple" , "Central or most important part of something" , "Central zone" , "Kernel" , "essential element" .)
'center' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for midst that I've seen before include "Where one is surrounded by other things" , "Among, amid" , "Centre" , "Blue dye; rainbow hue" , "In the middle of (archaic or literary)" .)
(Other definitions for rehab that I've seen before include "Treatment for dependency" , "Course of treatment for addicts" , "brief convalescence?" , "Restoration to health after, eg, addiction (colloq.)" , "A herb (anag.)" .)
(Other definitions for rec that I've seen before include "pleasure area" , "play area" , "Recreation ground (informal)" , "place for outdoor games" , "Sporting venue" .)
(Other definitions for sweetheart that I've seen before include "Beloved" , "One loved" , "Juliet had one" , "baby" , "Lover" .)