What sounds like vulgar series of lectures maybe (6)
I believe the answer is:
course
'series of lectures maybe' is the definition.
'what sounds like vulgar' is the wordplay.
'what sounds like' indicates a 'sounds like' (homophone) clue.
'vulgar' becomes 'coarse' ('coarse' can be a synonym of 'vulgar').
'coarse' is a homophone of 'COURSE'.
(Other definitions for course that I've seen before include "Route; lectures" , "Direction; lecture series" , "Route or meal segment" , "Mode, of action say" , "Flow" .)