Part of house finally being fit on completion (5,3)

I believe the answer is:

gable end

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'part of house' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

'finally being fit on completion' is the wordplay.
'finally' says to take the final letters.
'fit' becomes 'able' (similar in meaning).
'on' means one lot of letters go next to another.
'completion' becomes 'end' (I've seen this in another clue).
The last letter of 'being' is 'g'.
'g'+'able'+'end'='GABLE END'

Can you help me to learn more?

(Another definition for gable end that I've seen is " Pile of bricks".)

I've seen this clue in The Independent.

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