Mammal spreading fleas around ancient city (3,4)

I believe the answer is:

fur seal

'mammal' is the definition.
(fur seal is a kind of mammal)

'spreading fleas around ancient city' is the wordplay.
'spreading' indicates an anagram.
'around' means one lot of letters goes inside another.
'ancient city' becomes 'ur' (ancient Sumerian city state).
'fleas' is an anagram of 'fseal'.
'fseal' going around 'ur' is 'FUR-SEAL'.

I've seen this clue in The Daily Express.

Want a hint initially instead of a full solution? Install my app