Gardener resolved to plant thousand in shade (4,5)

I believe the answer is:

dark green

I'm a little stuck... Click here to teach me more about this clue!

'shade' is the definition.

'gardener resolved to plant thousand' is the wordplay.
I cannot quite see how this works, but
'thousand' could be 'k' (synonyms) and 'k' is located in the answer.
an anagram of 'gardener' is 'dargreen' which is within the left over letters.
No letters remain.
This explanation may well be incorrect...

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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