Foot, intact to start with, seen by a doctor (4)
I believe the answer is:
iamb
'foot' is the definition.
(type of metrical foot in poetry)
'intact to start with seen by a doctor' is the wordplay.
'to start with' says to take the initial letters.
'seen by' is a charade indicator (letters next to each other).
'doctor' becomes 'MB' (Bachelor of Medicine, Medicinae Baccalaureus).
The initial letter of 'intact' is 'i'.
'i'+'a'+'mb'='IAMB'
(Other definitions for iamb that I've seen before include "Short-long metric foot" , "Poet's foot" , "Line of verse" , "Metrical unit" , "Metrical foot of one short, one long syllables" .)