Mix socially with the biscuit (6)
I believe the answer is:
hobnob
'mix socially with the biscuit' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for hobnob that I've seen before include "Associate on familiar terms" , "Socialize, spend time with" , "Talk informally" , "Feasible" , "Hang out with people of standing" .)