Keep at it and your dog will fetch it! (5)
I believe the answer is:
stick
'keep' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for stick that I've seen before include "Staff - criticism" , "Glue; piece of wood" , "Adhere - cane" , "Tolerate" , "Switch < put up" .)