Rabbit on in bay at terminus (6)
I believe the answer is:
yatter
'rabbit on' is the definition.
(I've seen this before)
'in bay at terminus' is the wordplay.
'in' says the answer is hidden in the clue.
'YATTER' can be found hidden inside 'bay at terminus'.
(Other definitions for yatter that I've seen before include "Talk idly" , "Talk incessantly" , "Go on and on" , "Talk endlessly about nothing" , "jabber" .)