A missile from Uncle (3)

I believe the answer is:

sam

This clue is a double definition.

'a missile' is the first definition.
(abbreviation for surface-to-air missile)

'uncle' is the second definition.
(Uncle Sam is an example)

'from' acts as a link.

(Other definitions for sam that I've seen before include "Casablanca piano player" , "Boy" , "together once" , "Uncle" .)

I've seen this clue in the Evening Standard.

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