One line redacted in documents, working for old PM (6)

I believe the answer is:

wilson

I'm a little stuck... Click here to teach me more about this clue!

'pm' is the definition.
(I have seen 'Former PM' mean 'wilson' so perhaps 'pm' could also mean 'wilson')

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for wilson that I've seen before include "PM 1964-70, 74-76" , "9d [WHISTLE BLOWER]" , "Harold --, former PM" , "British PM, Harold - US President, Woodrow" , "Harold -, UK PM" .)

I've seen this clue in The Telegraph.

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