I'm not one to weaken (6)

I believe the answer is:

impair

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

'weaken' is the definition.
(I've seen this in another clue)

'i'm not one to' is the wordplay.
'i'm' becomes 'iam' (I've seen this in other clues).
'not' is a deletion indicator.
'one' becomes 'a' (a thing is one thing).
'to' becomes 'pair' (I can't justify this - if you can you should believe this answer much more).
'iam' with 'a' taken out is 'im'.
'im'+'pair'='IMPAIR'

Can you help me to learn more?

(Other definitions for impair that I've seen before include "blunt" , "Make worse or less effective" , "Spoil strength, quality of" , "Damage or handicap" , "Courteous man (colloq.)" .)

I've seen this clue in The Globe and Mail and The Irish News.

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