Among French heads, a conversation (4-1-4)
I believe the answer is:
tete-a-tete
'conversation' is the definition.
(I know that tete-a-tete is a type of conversation)
'among french heads a' is the wordplay.
'among' indicates putting letters inside (inserted letters are placed among others).
'french heads' becomes 'tete tete' ('tete' is 'head' in French).
'tetetete' placed around 'a' is 'TETE-A-TETE'.
(Other definitions for tete-a-tete that I've seen before include "Private couple's conversation" , "Private meeting" , "Private conversation between two French people" , "Private conversation between two people as in France" , "Informal chat" .)