Ostentatious rain-maker losing face (4)
I believe the answer is:
loud
'ostentatious' is the definition.
(I've seen this in another clue)
'rain-maker losing face' is the wordplay.
'rain maker' becomes 'cloud' (I've seen this in another clue).
'losing face' means to remove the first letter.
'cloud' with its initial letter taken off is 'LOUD'.
(Other definitions for loud that I've seen before include "like the bees in Yeats's glade?" , "Resounding" , "Deafening" , "vulgar" , "This speaker is" .)