6d Atmosphere in office, initially gloomy (5) O?O?R ODOUR (O +DOUR)
4d Visitor figured in conversation (5) G?E?T GUEST Can see visitor but not conversation.
13d Blaze under bridge, something one doesn't want to be caught in (9)
C?G?S?I?E
20d Admit academic robe's no good at university (5) O?N?O (OWNTO)