Retiree missing start of soap? (15)

I believe the answer is:

oldagepensioner

I'm a little stuck... Click here to teach me more about this clue!

'soap?' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'retiree missing start' is the wordplay.
'retiree' becomes 'pensioner' (I've seen this before).
'missing' becomes 'oldage' (I can't explain this - if you can you should believe this answer much more).
'start' says to put letters next to each other.
'pensioner' put after 'oldage' is 'OLDAGEPENSIONER'.

'of' acts as a link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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