Lament, i.e. bawl, when upset (6)
I believe the answer is:
bewail
'lament' is the definition.
('bewail' can be a synonym of 'lament')
'i e bawl when upset' is the wordplay.
'when upset' indicates anagramming the letters.
'i'+'e'+'bawl'='iebawl'
'iebawl' with letters rearranged gives 'BEWAIL'.
(Other definitions for bewail that I've seen before include "Greatly lament" , "Express grief" , "Loudly regret" , "Goose-liver pate" , "Cry over, mourn for" .)