Topic those people echo (5)
I believe the answer is:
theme
'topic' is the definition.
(synonyms)
'those people echo' is the wordplay.
'those people' becomes 'them' ('they' refers to a group of people).
'echo' becomes 'e' (phonetic alphabet: alpha, bravo, charlie etc.).
'them'+'e'='THEME'
(Other definitions for theme that I've seen before include "Topic for discussion" , "Motif - 4 across" , "Subject matter, motif" , "Short melody" , "idea of the work" .)