Cross and vulgar in audition (4)
I believe the answer is:
rood
'cross' is the definition.
(term for a crucifix)
'vulgar in audition' is the wordplay.
'vulgar' becomes 'rude' (vulgar can mean rude or gross).
'in audition' shows a homophone (sound like) (audition can mean hearing).
'rude' is a homophone of 'ROOD'.
'and' acts as a link.
(Other definitions for rood that I've seen before include "old piece of land" , "Crucifix - old unit of area" , "- Loft; - screen" , "Crucifix on door" , "Pole, perch or crucifix" .)