Mother goes to the doctor when in port (6)
I believe the answer is:
madras
'port' is the definition.
(Indian port)
'mother goes to the doctor when' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'goes to' means one lot of letters go next to another.
'the doctor' becomes 'dr' ('Dr' can be a synonym of 'doctor').
'when' becomes 'as'.
'ma'+'dr'+'as'='MADRAS'
'in' acts as a link.
(Other definitions for madras that I've seen before include "Indian city now known as Chennai, and medium hot curry" , "Tamil Nadu capital; a hottish curry" , "Fort St George (originally), Chennai (officially)" , "Kind of curry" , "place in Tamil Nadu" .)