Tea will put a smile on feelings of vexation (7)
I believe the answer is:
chagrin
'vexation' is the definition.
(I've seen this in another clue)
'tea will put a smile on feelings' is the wordplay.
I cannot quite understand how this works, but
'tea' could be 'cha' (cha is a type of tea) and 'cha' is found in the answer.
'smile' could be 'grin' (synonyms) and 'grin' is found in the answer.
No letters remain.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for chagrin that I've seen before include "Annoyance/shame at one's failure" , "Feeling of annoyance and disappointment" , "irritation?" , "Annoyance at having been humiliated" , "Shame at having failed" .)