People get Bertie no end upset! (5)
I believe the answer is:
tribe
'people' is the definition.
(a tribe is a group of people)
'bertie no end upset' is the wordplay.
'no end' means to remove the last letter.
'upset' indicates an anagram.
'bertie' with its final letter removed is 'berti'.
'berti' is an anagram of 'TRIBE'.
'get' is the link.
(Other definitions for tribe that I've seen before include "Traditional social group" , "social set" , "Ethnic grouping" , "Group of people; big family" , "Close-knit social group" .)