A lecturer welcoming king in dress (5)
I believe the answer is:
adorn
'dress' is the definition.
(I've seen this before)
'a lecturer welcoming king' is the wordplay.
'lecturer' becomes 'don' (don can mean an academic).
'welcoming' indicates putting letters inside (in sense of 'inviting in').
'king' becomes 'R' (abbreviation for rex, king in Latin).
'don' placed around 'r' is 'dorn'.
'a'+'dorn'='ADORN'
'in' acts as a link.
(Other definitions for adorn that I've seen before include "Beautify - decorate - enhance" , "get dressed!" , "Improve appearance" , "Bedeck" , "Festoon" .)