Pessimistic county defeated (8)
I believe the answer is:
downbeat
'pessimistic' is the definition.
(I've seen this before)
'county defeated' is the wordplay.
'county' becomes 'down' (County Down in Northern Ireland).
'defeated' becomes 'beat' (I've seen this in another clue).
'down'+'beat'='DOWNBEAT'
(Other definitions for downbeat that I've seen before include "Gloomy; laid-back" , "Miserable; relaxed" , "gesture by conductor" , "Low-key" , "Pessimistic; understated" .)