Design pencilled in, an elementary machine (8,5)

I believe the answer is:

inclined plane

'elementary machine' is the definition.
(basic ramp machine for lifting things)

'design pencilled in an' is the wordplay.
'design' indicates an anagram.
'pencilled'+'in'+'an'='pencilledinan'
'pencilledinan' with letters rearranged gives 'INCLINED PLANE'.

I've seen this clue in The Times.

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