Very quietly brought into AA, left in dismay (5)
I believe the answer is:
Here is my best explanation:
'dismay' is the definition.
('appal' can be a synonym of 'dismay')
'very quietly brought into aa left' is the wordplay.
'very quietly' becomes 'pp'.
'brought into' is an insertion indicator.
'left' becomes 'l' (common abbreviation).
'pp' inserted within 'aa' is 'appa'.
'in' is the link.
(Other definitions for appal that I've seen before include "Cause to be unpleasantly surprised", "Outrage", "Put at rest (suspicion)", "To shock, dismay", "exhibiting dismay", "Scandalise", "Dismay, horrify", "Disgust", "Greatly dismay" and "outrage".)