Tom, right on the tail of his victim? (6)
I believe the answer is:
mouser
This clue might be a double definition.
'tom' is the first definition.
(thesaurus)
'right on the tail of his victim?' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
Can you help me to learn more?
(Other definitions for mouser that I've seen before include "Cat proficient at catching small rodents" , "Predatory cat" , "Cat that's good at catching small rodents" , "Cat as hunter of small rodents" , "One getting rid of vermin" .)