Suppose Sammy lost his medal! (3)

I believe the answer is:

say

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'suppose' is the definition.
('say' can be a synonym of 'suppose')

I don't understand the remainder of the clue.

(Other definitions for say that I've seen before include "Utter; e.g." , "Speak, utter" , "Judge" , "Articulate" , "Pronounce" .)

I've seen this clue in the Evening Standard.

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