Held in common (6)
I believe the answer is:
mutual
'held in common' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for mutual that I've seen before include "Dickens novel 'Our . . . . . . Friend'" , "Reciprocal or shared, like friendship" , "Common to two or more" , "building society, say" , "Reciprocal; common" .)