Those people beginning to eat a Topic? (5)
I believe the answer is:
theme
'a topic?' is the definition.
(I know that topic can be written as theme)
'those people beginning to eat' is the wordplay.
'those people' becomes 'them' ('they' refers to a group of people).
'beginning to' indicates taking the first letters.
The first letter of 'eat' is 'e'.
'them'+'e'='THEME'
(Other definitions for theme that I've seen before include "Musical motif" , "Topic for discussion" , "Musical idea; topic" , "The main sound" , "Motif - 4 across" .)