Facilities costing extra, landlord leaving note (4,4,6)

I believe the answer is:

dear john letter

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'facilities costing' is the definition.
The definition suggests a singular noun which matches the answer.

'extra landlord leaving note' is the wordplay.
'extra landlord leaving' becomes 'dearjohn' (I am not sure about this - if you are sure you should believe this answer much more).
'note' becomes 'letter' (I've seen this in another clue).
'dearjohn'+'letter'='DEAR JOHN LETTER'

Can you help me to learn more?

(Other definitions for dear john letter that I've seen before include "Rejection" , "chucking post" , "for Augustus or Gwen?" , "note ending a relationship" , "Final, formal brush-off" .)

I've seen this clue in The Independent.

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