Princess loses heart to sign up part (7)

I believe the answer is:

disjoin

'part' is the definition.
(I know this)

'princess loses heart to sign up' is the wordplay.
'princess' becomes 'di' (Princess Diana).
'heart' indicates the central letters.
'to sign up' becomes 'join' (I've seen this before).
The central letter of 'loses' is 's'.
'di'+'s'+'join'='DISJOIN'

(Another definition for disjoin that I've seen is " Separate".)

I've seen this clue in the Sydney Morning Herald.

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