Monotonously lengthy formation of rust (4)

I believe the answer is:

ruts

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'monotonously lengthy formation of rust' is the definition.
I can't judge whether this definition defines the answer.

'of rust' is the wordplay.
'of' indicates anagramming the letters (the answer comes from or 'of' the letters).
'rust' is an anagram of 'RUTS'.

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(Other definitions for ruts that I've seen before include "Deep tracks in paths" , "Grooves in the ground" , "Deep furrows" , "Deep tracks in path" , "gets ready for new partner" .)

I've seen this clue in the Evening Standard.

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