Enemy agents sheltering city group (7)

I believe the answer is:

species

I'm a little stuck... Click here to teach me more about this clue!

'group' is the definition.
(eg group of animals)

'enemy agents sheltering city' is the wordplay.
'enemy agents' becomes 'spies' (secret agents. I am not sure about the 'enemy' bit.).
'sheltering' means one lot of letters goes inside another.
'city' becomes 'EC' (the City of London postcode).
'spies' going around 'ec' is 'SPECIES'.

Can you help me to learn more?

(Other definitions for species that I've seen before include "Biological group" , "Kind of creature" , "Groups of related plants or animals" , "Taxonomic group capable of interbreeding" , "Variety, taxonomic group" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.