Irregular Neptune-Venus transit (6)

I believe the answer is:

uneven

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

'irregular' is the definition.
(similar in meaning)

'neptune-venus transit' is the wordplay.
'UNEVEN' is hidden within the letters.
However, I am uncertain how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for uneven that I've seen before include "Bumpy - odd" , "Not smooth or flat" , "Inconsistant in quality" , "Rough on the surface" , "Not level or smooth" .)

I've seen this clue in the Sydney Morning Herald.

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