Tea before a smile of embarrassment (7)
I believe the answer is:
chagrin
'embarrassment' is the definition.
(I know that chagrin is a type of embarrassment)
'tea before a smile' is the wordplay.
'tea' becomes 'cha' (cha is a type of tea).
'before' is a charade indicator (letters next to each other).
'a smile' becomes 'grin' (synonyms).
'cha'+'grin'='CHAGRIN'
'of' acts as a link.
(Other definitions for chagrin that I've seen before include "Disappointment, exasperation" , "Humiliation, mortification" , "Arching with annoyed disappointment" , "irritation?" , "Shame at having failed" .)