Secretary beginning to loathe friend (3)
I believe the answer is:
pal
'friend' is the definition.
(pal can mean a friend)
'secretary beginning to loathe' is the wordplay.
'secretary' becomes 'PA' (abbreviation for personal assistant).
'beginning to' indicates taking the first letters.
The first letter of 'loathe' is 'l'.
'pa'+'l'='PAL'
(Other definitions for pal that I've seen before include "Friend (colloq.)" , "Brother" , "Mate, informal friend" , "China" , "Buddy, chum" .)