Second lot disconcertingly emotionless (5-4)

I believe the answer is:

stone-cold

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

'emotionless' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?

'second lot disconcertingly' is the wordplay.
'second lot' anagrams to 'STONE-COLD'.
Though, I'm unsure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for stone-cold that I've seen before include "At a low temperature" , "Having lost all warmth" , "Absolutely without heat" .)

I've seen this clue in The Mirror.

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