Mercator's pet? (3)
I believe the answer is:
cat
'pet?' is the definition.
(cats are often kept as pets)
'mercator's' is the wordplay.
'CAT' is hidden within the letters.
However, I am unsure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for cat that I've seen before include "Lash < jazz fan" , "An old whip with nine tails" , "one's pyjamas? They're an excellent thing" , "Feline mammal" , "See 23" .)