Something penned by William Blake? (4)

I believe the answer is:

iamb

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'something penned by william blake?' is the definition.
I can't tell whether this definition defines the answer.

'penned by william blake?' is the wordplay.
'penned by' indicates a hidden word.
'IAMB' can be found hidden inside 'william blake'.

Can you help me to learn more?

(Other definitions for iamb that I've seen before include "Poet's foot" , "Line of verse" , "Short-long metrical foot" , "Part of a pentameter?" , "Short-long metric foot" .)

I've seen this clue in The Guardian.

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