One doctor in Australia is good for the foot (6)
I believe the answer is:
iambus
'for the foot' is the definition.
(iambus is a kind of foot)
'one doctor in australia' is the wordplay.
'one' becomes 'i' (Roman numeral).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'in' means one lot of letters goes inside another.
'australia' becomes 'aus' (abbreviation).
'mb' going into 'aus' is 'ambus'.
'i'+'ambus'='IAMBUS'
'is good' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for iambus that I've seen before include "Metrical foot" , "poetic form" , "Type of metrical unit in a poem" , "Metrical unit of two syllables" .)