She shows Ken possesses a warm heart (5)
I believe the answer is:
karen
'she' is the definition.
'ken possesses a warm heart' is the wordplay.
'possesses' means one lot of letters goes inside another.
'heart' says to take the centre.
The middle letters of 'warm' are 'ar'.
'ken' enclosing 'ar' is 'KAREN'.
'shows' is the link.
(Other definitions for karen that I've seen before include "oriental language" , "Girl" , "Girl's name - ethnic Thai in Burma" , "Carpenter of note" , "One at home in 15 across [AARHUS]" .)