Mingle in the enclosure (8)
I believe the answer is:
compound
I believe this clue is a double definition.
'mingle' is the first definition.
(I know this)
'the enclosure' is the second definition.
(compound is a kind of enclosure)
'in' is the link.
(Other definitions for compound that I've seen before include "Whole formed by two or more elements" , "Add on to" , "A mix of ingredients" , "Blended substance - enclosed area" , "Kind of interest accumulating on capital plus interest" .)