Insignificant duke's a weakling (4)

I believe the answer is:

weed

'a weakling' is the definition.

'insignificant duke's' is the wordplay.
'insignificant' becomes 'wee'.
'duke' becomes 'd' (abbreviation).
'wee'+'d'='WEED'

(Other definitions for weed that I've seen before include "Ineffectual person" , "Made water" , "Hoe to remove it" , "Work in garden" , "Went" .)

I've seen this clue in The Guardian.

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