Extra small sleepwear for Spooner (4)

I believe the answer is:

tiny

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'extra small' is the definition.
'tiny' can be an answer for 'small' (similar in meaning). I'm not sure about the 'extra' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for tiny that I've seen before include "Extremely small" , "Minuscule" , "Quite insignificant" , "pocket" , "with sharp points?" .)

I've seen this clue in The Independent.

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