Crossword Genius

Unusual tone on photo developed in the usual place (7)

Ross

I believe the answer is:

entopic

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

'unusual' is the definition.
Both the answer and definition are adjectives.
Perhaps there's a link between them I don't understand?

I can't explain the remainder of the clue.

Can you help me to learn more?

I've seen this clue in The Sunday Times and The Times.
Want a hint initially instead of a full solution? Install my app