Bones; star shaped next to his heart (5)
I believe the answer is:
tarsi
'bones' is the definition.
(bones of the foot)
'star shaped next to his heart' is the wordplay.
'shaped' indicates anagramming the letters.
'next to' says to put letters next to each other.
'heart' means to look at the middle letters.
The centre of 'his' is 'i'.
'star' is an anagram of 'tars'.
'tars'+'i'='TARSI'
(Other definitions for tarsi that I've seen before include "parts of leg" , "Foot bones" , "Parts of skeleton" , "Ankle bones" , "collections of bones?" .)