Prime object of care (6)
I believe the answer is:
charge
I believe this is a triple definition!
'prime' is the first definition.
(thesaurus)
'object' is the second definition.
(charge is a kind of object)
'of' is a link.
'care' is the third definition.
(I know that care can be written as charge)
(Other definitions for charge that I've seen before include "Fill; fee" , "Formal accusation" , "Sortie" , "Deliver an official injunction" , "Legal accusation" .)