Number set about making the interior look gay (7)

I believe the answer is:

festive

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'look gay' is the definition.
'festive' can be an answer for 'gay' (thesaurus). I'm unsure of the 'look' bit.

'number set about making the interior' is the wordplay.
'number' becomes 'five' (five is a kind of number).
'set about making' becomes 'est' (I can't justify this - if you can you should give a lot more credence to this answer).
'the interior' is an insertion indicator.
'five' placed around 'est' is 'FESTIVE'.

Can you help me to learn more?

(Other definitions for festive that I've seen before include "Christmassy" , "Jolly" , "Celebratory, joyful" , "Merry" , "Gay" .)

I've seen this clue in The Globe and Mail.

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