Whip pet (3)
I believe the answer is:
cat
This clue is a double definition.
'whip' is the first definition.
(cat o' nine tails, cat for short is a type of whip)
'pet' is the second definition.
(cats are often kept as pets)
(Other definitions for cat that I've seen before include "An old whip with nine tails" , "See 23" , "one's pyjamas? They're an excellent thing" , "Tabby" , "A tom" .)