Passed out at end if upset (7)
I believe the answer is:
fainted
'passed out' is the definition.
('faint' can be a synonym of 'pass out')
'at end if upset' is the wordplay.
'upset' indicates anagramming the letters.
'at'+'end'+'if'='atendif'
'atendif' is an anagram of 'FAINTED'.
(Other definitions for fainted that I've seen before include "Swooned, lost consciousness" , "Passed out" .)