Keep talking in mob (5)
I believe the answer is:
horde
'mob' is the definition.
(horde can mean a mob or crowd of people)
'keep talking' is the wordplay.
'keep' becomes 'hoard' (I've seen this before).
'talking' shows a homophone (sound like).
'hoard' is a homophone of 'HORDE'.
'in' is the link.
(Other definitions for horde that I've seen before include "A swarm or multitude" , "Large force" , "Nomadic army" , "Throng, mass" , "Vast multitude" .)