A Bachelor of Medicine getting one on one's feet (5)
I believe the answer is:
Here is my best explanation:
'feet' is the definition.
(iamb is a kind of foot)
'a bachelor of medicine getting one on one's' is the subsidiary indication.
'bachelor of medicine' becomes 'mb' ('MB' can be a synonym of 'bachelor of medicine').
'getting' says to put letters next to each other.
'one' becomes 'i' (roman numeral).
'on' says to put letters next to each other.
'one's' becomes 'i' (I've seen this in other clues).
'a'+'mb' is 'amb'.
'ambi' after 'i' is 'iambi'.
(Other definitions for iambi that I've seen before include "Concierto de Aranjuez composer", "Feet of two syllables (one short and one long)", "Short-long metrical feet", "Metrical units with alternating long and short syllables", "Poetic pieces", "Poetic feet", "Metrical feet" and "Film theatre".)