Crossword Genius

In the words of the peacemaker, add ice (4,2)

Ross

I believe the answer is:

cool it

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

'in the words of the peacemaker add' is the definition.
I can't tell whether this defines the answer.

'ice' is the wordplay.
I cannot quite understand how this works, but
'ice' could be 'cool' (I've seen this in another clue) and 'cool' is located in the answer.
The remaining letters 'it' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for cool it that I've seen before include "Here's what to do before opening champagne" , "Don't get so excited'" , "Relax" , "Modern injunction to calm down" , "Calm down - not so hot." .)

I've seen this clue in the Evening Standard.
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