Foreman who makes mistakes? (6)

I believe the answer is:

gaffer

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

'foreman' is the definition.
(I know that foreman can be written as gaffer)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for gaffer that I've seen before include "Old man" , "Chief electrician on a film set" , "Informal boss or foreman" , "Senior electrician on a film/TV set" , "blunderer" .)

I've seen this clue in The Irish Independent.

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