Had hallucinations, as carpenters are wont to do (3,6)

'had hallucinations' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'as carpenters are wont to do' is the wordplay.
I cannot quite see how this works, but
'as' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?