Loathing headgear friend regularly displayed (6)
I believe the answer is:
hatred
'loathing' is the definition.
(I've seen this before)
'headgear friend regularly displayed' is the wordplay.
'headgear' becomes 'hat' (hat is a kind of headgear).
'regularly displayed' indicates alternate letters (letters selected on a regular basis).
The alternate letters of 'friend' are 'red'.
'hat'+'red'='HATRED'
(Other definitions for hatred that I've seen before include "Great dislike" , "'Loathing, enmity (6)'" , "Dearth (anag)" , "Extreme dislike and enmity" , "Violent emotion" .)