Fret in the past, brought up in south-east (7)
I believe the answer is:
agonise
'fret' is the definition.
(both can mean to worry or dread)
'past brought up in south-east' is the wordplay.
'past' becomes 'ago' (similar in meaning).
'brought up' says the letters should be written in reverse (in a down clue, letters go up).
'south east' becomes 'SE' (abbreviation).
'in' back-to-front is 'ni'.
'ago'+'ni'+'se'='AGONISE'
'in the' acts as a link.
(Other definitions for agonise that I've seen before include "Suffer anguish - go in sea (anag)" , "Be very worried" , "Suffer torment" , "Suffer extreme mental pain" , "Labour" .)