Tyrant captures northern retreat -- it's hopeless (10)
I believe the answer is:
despondent
'hopeless' is the definition.
('despondent' can be similar in meaning to 'hopeless')
'tyrant captures northern retreat' is the wordplay.
'tyrant' becomes 'despot' ('despot' can be a synonym of 'tyrant').
'captures' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'retreat' becomes 'den'.
'n'+'den'='nden'
'despot' enclosing 'nden' is 'DESPONDENT'.
'it's' acts as a link.
(Other definitions for despondent that I've seen before include "Heartsick" , "Down in the dumps" , "In low spirits" , "Downcast" , "Despairing" .)