Favourite hamster, say (3)
I believe the answer is:
pet
This clue is a double definition.
'favourite' is the first definition.
(synonyms)
'hamster say' is the second definition.
(hamsters are often kept as pets)
(Other definitions for pet that I've seen before include "Favoured child or animal" , "Favourite, darling" , "Darling; fit of sulks" , "Favourite or house animal" , "House animal; sulk" .)