Upset gown first internally (8)
I believe the answer is:
distress
'upset' is the definition.
(distressing is a kind of upseting)
'gown first internally' is the wordplay.
'gown' becomes 'dress' (gown is a kind of dress).
'first' becomes 'ist' (ist resembles 1st).
'internally' indicates putting letters inside.
'dress' going around 'ist' is 'DISTRESS'.
(Other definitions for distress that I've seen before include "Extreme pain, poverty" , "Severe pain" , "Cause mental pain" , "State of anxiety or woe" , "Extreme anxiety or sorrow" .)