So the new head is a relative (3)

I believe the answer is:

son

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

'so the new head' is the wordplay.
'head' says to take the initial letters.
The initial letter of 'new' is 'n'.
'so'+'n'='SON'

(Other definitions for son that I've seen before include "Human offspring" , "Heir" , "A relative" , "Young boy" , "Native" .)

I've seen this clue in the Evening Standard.

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