Gross things that look ultimately at least interesting (7)

I believe the answer is:

greyest

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

'ultimately at least interesting' is the definition.
I can't tell whether this definition defines the answer.

'gross things that look' is the wordplay.
I cannot really understand how this works, but
'look' could be 'eye' (eyeing is a kind of looking) and 'eye' is present in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Another definition for greyest that I've seen is " most dull".)

I've seen this clue in The Times.

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