Play down reunited team's playing (13)

I believe the answer is:

underestimate

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'play down' is the definition.
Although both the answer and definition are verbs in their base form, I can't understand how one could define the other.

'reunited team's playing' is the wordplay.
'playing' indicates an anagram.
'reunited'+'teams'='reunitedteams'
'reunitedteams' anagrammed gives 'UNDERESTIMATE'.

Can you help me to learn more?

(Other definitions for underestimate that I've seen before include "Low guess" , "Sell short" , "inaccurate" , "Rate as too low" , "Evaluation that is too low" .)

I've seen this clue in The Telegraph.

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