Lady’s passionate in the morning (5)
I believe the answer is:
madam
'lady's' is the definition.
(synonyms)
'passionate in the morning' is the wordplay.
'passionate' becomes 'mad'.
'in the morning' becomes 'am'.
'mad'+'am'='MADAM'
(Other definitions for madam that I've seen before include "formidable woman" , "Woman running a brothel" , "'Call Me ---' (I. Berlin)" , "pompous young lady?" , "Woman of standing" .)