Fed up, having worry, one good soul having negative attitude (9)
I believe the answer is:
defeatist
'negative attitude' is the definition.
'defeatist' can be an answer for 'negative' (thesaurus). I'm not certain of the 'attitude' bit.
'fed up having worry one good soul' is the wordplay.
'fed up' becomes 'def' ('fed' going up in a down clue).
'having' means one lot of letters go next to another.
'worry' becomes 'eat' (eating is a kind of worrying).
'one good soul' becomes 'ist' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'def'+'eat'+'ist'='DEFEATIST'
'having' is the link.
Can you help me to learn more?
(Other definitions for defeatist that I've seen before include "He's always expecting to be beaten" , "With this attitude, one is resigned to failure" , "If date set (anag.)" , "Attitude that failure is inevitable" , "One expects frustration" .)