As loose dogs may be, or doctors driven to patients, do we hear? (7,2,4)

'as loose dogs may be' is the definition.
(a dog might be brought to heel by its owner)

'doctors driven to patients do we hear?' is the wordplay.
I cannot really see how this works, but
'to' is found in the answer.
'we hear?' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
This may be the basis of clue (or it may be nonsense).

'or' is the link.