Hold forth, having failed medical (7)
I believe the answer is:
declaim
'hold forth' is the definition.
(I've seen this before)
'failed medical' is the wordplay.
'failed' indicates anagramming the letters.
'medical' with letters rearranged gives 'DECLAIM'.
'having' acts as a link.
(Other definitions for declaim that I've seen before include "Utter rhetorically" , "Speak boldly" , "Rail against" , "Medical (anag)" , "Hold forth" .)