Craft device for turning hard wood (4)

I believe the answer is:

helm

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

'craft device for turning' is the definition.
I can't judge whether this definition defines the answer.

'hard wood' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'wood' becomes 'elm' (elm is a type of tree).
'h'+'elm'='HELM'

Can you help me to learn more?

(Other definitions for helm that I've seen before include "Steering device" , "Position of leadership" , "Part of ship" , "Tiller; steer" , "Tiller; old headgear" .)

I've seen this clue in The Sunday Times and The Times.

Want a hint initially instead of a full solution? Install my app