In a plum position, ancestor-wise? (4,2,3,6)

'in a plum position ancestor-wise?' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'in a plum position ancestor-wise?' is the wordplay.
I cannot quite understand how this works, but
'in' is within the answer.
'wise?' could be 'hep' (I've seen this in another clue) and 'hep' is found in the answer.
This explanation may well be incorrect...