With reserve in Mafia country when son's missing (5)

I believe the answer is:

icily

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

I don't understand the remainder of the clue.

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(Other definitions for icily that I've seen before include "Coldly" , "In a chilling manner" , "in unfriendly way" , "In a frosty manner" , "Without feeling" .)

I've seen this clue in The Telegraph.

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