Crossword Genius

Moderates shouldn't lose them (7)

Ross

I believe the answer is:

tempers

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

'moderates' is the definition.
(I know this)

'shouldn't lose them' is the wordplay.
I cannot really see how this works, but
'them' could be 'em' (abbreviation) and 'em' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for tempers that I've seen before include "Hardens steel" , "Hardens metal by heating and cooling" .)

I've seen this clue in The Globe and Mail.
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