Difficult sort of test for banks that's nearly complete (9)
I believe the answer is:
stressful
'difficult' is the definition.
(thesaurus)
'sort of test for banks that's nearly complete' is the wordplay.
'sort of test for banks' becomes 'stress' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'that's nearly' means to remove the last letter.
'complete' becomes 'full' (similar in meaning).
'full' with its last letter taken away is 'ful'.
'stress'+'ful'='STRESSFUL'
Can you help me to learn more?
(Other definitions for stressful that I've seen before include "under great pressure" , "Creating tension" , "Worrying" , "Causing mental tension" , "Very hard on the nerves" .)