Boat takes doctor from Moscow (4)
I believe the answer is:
scow
'boat' is the definition.
(I know that scow is a type of boat)
'doctor from moscow' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'from' indicates named letters should be taken away.
'moscow' with 'mo' removed is 'SCOW'.
'takes' is the link.
(Other definitions for scow that I've seen before include "Unpowered freight barge" , "Maybe lighter" , "Wide-beamed dinghy" , "ighter" , "Vessel" .)