Crossword Genius

No big building complex open (5)

Ross

I believe the answer is:

unlid

I'm a little stuck... Click here to teach me more about this clue!

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

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Another definition for unlid that I've seen is " Open".)

I've seen this clue in The Times and The Sunday Times.
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