The gardener's little room? (3)

I believe the answer is:

den

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

'room?' is the definition.
(I know that den is a type of room)

'the gardener's little' is the wordplay.
'DEN' is hidden within the letters.
However, I am not sure how this is indicated.

Can you help me to learn more?

(Other definitions for den that I've seen before include "Animal's home or gent's study" , "Room for work or play" , "Lair for animal or study for gent" , "Animal lair or gent's study" , "Wild animal's lair" .)

I've seen this clue in the Evening Standard.

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