This dog's odds double (8)
I believe the answer is:
springer
'this dog's' is the definition.
(I've seen this before)
'odds double' is the wordplay.
'odds' becomes 'sp' (betting abbreviation for starting price).
'double' becomes 'ringer' (I've seen this before).
'sp'+'ringer'='SPRINGER'
(Other definitions for springer that I've seen before include "Type of spaniel" , "Shown [AT CRUFTS]" , "Kind of spaniel" , "Game dog" , "A bounder" .)