The prototype of an oil rig installation (8)

I believe the answer is:

original

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'the prototype' is the definition.
(I've seen this before)

'an oil rig installation' is the wordplay.
'an oil rig' can be anagrammed to 'ORIGINAL'.
Though, I am unsure how this is indicated.

'of' is the link.

Can you help me to learn more?

(Other definitions for original that I've seen before include "First, earliest" , "Never seen or performed before" , "Prototype" , "Existing from the start - quite new" , "An oil rig (anag)" .)

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

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