Foot doctor in Iowa, America (6)
I believe the answer is:
iambus
'foot' is the definition.
(iambus is a kind of foot)
'doctor in iowa america' is the wordplay.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'in' indicates putting letters inside.
'iowa' becomes 'ia' (standard US state two-letter abbreviation).
'america' becomes 'us' (abbreviation for the United States).
'ia'+'us'='iaus'
'mb' placed into 'iaus' is 'IAMBUS'.
(Other definitions for iambus that I've seen before include "Metrical unit of two syllables" , "Type of metrical unit in a poem" , "Metrical foot" , "poetic form" .)