Doctor joining European ship in black tie? (5)
I believe the answer is:
dress
'black tie?' is the definition.
(black tie is a kind of dress)
'doctor joining european ship' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'joining' means one lot of letters go next to another.
'european' becomes 'E' (abbreviation e.g. EU).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'dr'+'e'+'ss'='DRESS'
'in' is the link.
(Other definitions for dress that I've seen before include "changing gear" , "Gown" , "One-piece garment" , "clean > bandage" , "clobber" .)