At the outset friendly and tactful with girl’s Dad (6)
I believe the answer is:
father
'dad' is the definition.
(I've seen this in another clue)
'at the outset friendly and tactful with girl's' is the wordplay.
'at the outset' indicates taking the first letters (the outset is the beginning).
'with' says to put letters next to each other.
'girl' becomes 'her' ('her' refers to a girl or woman).
The initial letters of 'friendly and tactful' is 'fat'.
'fat'+'her'='FATHER'
(Other definitions for father that I've seen before include "Male parent" , "PA" , "Progenitor" , "Parent; priest" , "Sire" .)