Behind swamp spoil one yellow flower (5,8)

I believe the answer is:

marsh marigold

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'flower' is the definition.
(thesaurus)

'behind swamp spoil one yellow' is the wordplay.
'behind swamp' becomes 'marsh' (I've seen this before. I am not sure about the 'behind' bit.).
'spoil' becomes 'mar' (synonyms).
'one' becomes 'i' (Roman numeral).
'yellow' becomes 'gold' (gold is a kind of yellow).
'marsh'+'mar'+'i'+'gold'='MARSH MARIGOLD'

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(Other definitions for marsh marigold that I've seen before include "Kingcup" , "Water-loving plant of buttercup family" .)

I've seen this clue in The Telegraph.

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