Smile after tea shows annoyance (7)
I believe the answer is:
chagrin
'annoyance' is the definition.
(I've seen this before)
'smile after tea' is the wordplay.
'smile' becomes 'grin' (grinning is a kind of smiling).
'after' says to put letters next to each other.
'tea' becomes 'cha' (cha is a type of tea).
'grin' after 'cha' is 'CHAGRIN'.
'shows' acts as a link.
(Other definitions for chagrin that I've seen before include "Shame at one's failure" , "Humiliation, mortification" , "Embarrassment - rich nag (anag)" , "Feeling of annoyance and embarrassment" , "Acute annoyance or disappointment" .)