Being a good mate, will wash up (3)

I believe the answer is:

pal

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'being' is the definition.
(I know that pal is a type of friend)

I don't understand how the remainder of the clue works.

(Other definitions for pal that I've seen before include "Mate, informal friend" , "Brother" , "China" , "Mate, buddy" , "Buddy, chum" .)

I've seen this clue in the Evening Standard.

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