how do i remove black gunk from the drum?

Hi everyone

Indesit Washing Machine WIXL 123 UK


For the past week every time I take my washing out of the washer I have black imprinted drum marks on my clothes. And now it starting to come out in clumps too, all over my washing.

I have tried an empty cycle on a 60 deg wash, with detergent. then straight after the same again but without detergent.

I am at my wits end now, can anyone please advise me what I can do. many thanks in advance