Doctor in beer walk (5)
I believe the answer is:
amble
'walk' is the definition.
(amble is a kind of walk)
'doctor in beer' is the wordplay.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus**).
'in' means one lot of letters goes inside another.
'beer' becomes 'ale' (I've seen this before).
'mb' placed inside 'ale' is 'AMBLE'.
(Other definitions for amble that I've seen before include "Toddler does this" , "Blame for slow walk" , "promenade" , "Go at a leisurely gait" , "Walk in a leisurely fashion" .)