Crossword Genius

It's opposed to cleaner receiving casual welcome (8)

Ross

I believe the answer is:

filthier

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

'it's opposed to cleaner receiving casual' is the definition.
I can't tell whether this defines the answer.

'welcome' is the wordplay.
I cannot really understand how this works, but
'welcome' could be 'hi' (both are greetings) and 'hi' is present in the answer.
The remaining letters 'filter' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?

(Another definition for filthier that I've seen is " Disgustingly dirtier".)

I've seen this clue in The Irish Times.
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