Center
'center' is the definition.
(I know that center can be written as core)
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 the entire 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" .)