Companion given a smile, causing annoyance (7)
I believe the answer is:
chagrin
'annoyance' is the definition.
(I've seen this before)
'companion given a smile' is the wordplay.
'companion' becomes 'cha' (I've seen this in other clues).
'given' means one lot of letters go next to another.
'a smile' becomes 'grin' ('grin' can be a synonym of 'smile').
'cha'+'grin'='CHAGRIN'
'causing' acts as a link.
(Other definitions for chagrin that I've seen before include "Humiliation, mortification" , "Discomfiture" , "Emotion" , "Arching with annoyance and embarrassment" , "Acute annoyance or disappointment" .)