South African Lieutenant’s agreement to limit launchers (4)

I believe the answer is:

salt

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'agreement to limit launchers' is the definition.
I can't tell whether this defines the answer.

'south african lieutenant's' is the wordplay.
'south african' becomes 'sa'.
'lieutenant' becomes 'lt' (abbreviation for lieutenant).
'sa'+'lt'='SALT'

Can you help me to learn more?

(Other definitions for salt that I've seen before include "Preservative" , "Mariner; sodium chloride" , "Crystalline substance used to season food" , "Wit; sodium chloride" , "White crystalline substance" .)

I've seen this clue in The Hindu.

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