Forestall old boy through note (7)

I believe the answer is:

obviate

'forestall' is the definition.
(I've seen this before)

'old boy through note' is the wordplay.
'old boy' becomes 'ob'.
'through' becomes 'via' (I've seen this before).
'note' becomes 'te'.
'ob'+'via'+'te'='OBVIATE'

(Other definitions for obviate that I've seen before include "Preclude" , "Remove (a need or difficulty)" , "Anticipate" , "Avoid (impending problem)" , "Forestall" .)

I've seen this clue in The Telegraph.

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