Crossword Genius

Mercian king returning by wild desert covered in greenery (10)

Ross

I believe the answer is:

afforested

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'covered in greenery' is the definition.
The answer and definition can be both to do with contact as well as being past participle verbs.
Perhaps there's a link between them I don't understand?

'mercian king returning by wild desert' is the wordplay.
'mercian king' becomes 'offa' (I've seen this before).
'returning' says the letters should be written backwards.
'by' says to put letters next to each other.
'wild' indicates an anagram.
'offa' in reverse letter order is 'affo'.
'desert' anagrammed gives 'rested'.
'affo'+'rested'='AFFORESTED'

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I've seen this clue in The Times.
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