Doctor in Iowa, one for feet (5)
I believe the answer is:
iambi
'feet' is the definition.
(iamb is a kind of foot)
'doctor in iowa one' 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).
'one' becomes 'i' (Roman numeral).
'ia'+'i'='iai'
'mb' going inside 'iai' is 'IAMBI'.
'for' is the link.
(Other definitions for iambi that I've seen before include "Feet of two syllables (one short and one long)" , "Concierto de Aranjuez composer" , "Poetic feet" , "Film theatre" , "Metrical patterns" .)