Once yours truly’s heading inside, nearly everyone heads there (5)

I believe the answer is:

thine

'once yours' is the definition.
(thine historically meant what belongs to you)

'truly's heading inside nearly everyone heads there' is the wordplay.
'heads there' suggests taking the first letters (only the heads of the letters).
The initial letters of 'trulys heading inside nearly everyone' is 'THINE'.

(Another definition for thine that I've seen is " Yours (archaic)".)

I've seen this clue in The Times.

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