Contraption is breaking my back (5)

I believe the answer is:

gismo

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'contraption' is the definition.
(I've seen this in another clue)

'is breaking my back' is the wordplay.
'breaking' means one lot of letters goes inside another.
'my' becomes 'omg' (I can't justify this - if you can you should believe this answer much more).
'back' says the letters should be written in reverse.
'omg' written backwards gives 'gmo'.
'is' placed inside 'gmo' is 'GISMO'.

Can you help me to learn more?

(Other definitions for gismo that I've seen before include "Fancy device" , "Doofer" , "Ingenious gadget" , "Useful (but unspecified) device" , "Thingumajig - gadget" .)

I've seen this clue in The Times.

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