Awful grime around WC getting darker (8)

I believe the answer is:

gloomier

'darker' is the definition.
('gloomy' can be similar in meaning to 'dark')

'awful grime around wc' is the wordplay.
'awful' is an anagram indicator.
'around' indicates putting letters inside.
'wc' becomes 'loo' (both can mean a toilet).
'grime' anagrammed gives 'gmier'.
'gmier' placed around 'loo' is 'GLOOMIER'.

'getting' acts as a link.

(Another definition for gloomier that I've seen is " More morose or overcast".)

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