Personnel outside, worried by this loathsome character (5)
I believe the answer is:
hater
'this loathsome character' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'personnel outside worried' is the wordplay.
'personnel' becomes 'HR' (Human Resources).
'outside' means one lot of letters goes inside another (some letters go outside others).
'worried' becomes 'ate' (something worrying may eat someone up).
'hr' going around 'ate' is 'HATER'.
'by' is the link.
Can you help me to learn more?
(Other definitions for hater that I've seen before include "He loathes" , "One disliking" , "I really can't stand" , "One loathing" , "Antipathetic type" .)