Cat joins in conversation (4)
I believe the answer is:
lynx
'cat' is the definition.
(I've seen this before)
'joins in conversation' is the wordplay.
'joins' becomes 'links' ('link' can be a synonym of 'join').
'in conversation' shows a homophone (sound like).
'links' sounds like 'LYNX'.
(Other definitions for lynx that I've seen before include "Animal that's spotted" , "European wild cat" , "Keen-eyed cat" , "Wild cat with yellowish-brown fur and tufted ears" , "One with sharp eyes" .)