Trying brass on shelved storage (5-7)
I believe the answer is:
nerve-racking
'trying' is the definition.
(I know that trying can be written as nerve-racking)
'brass on shelved storage' is the wordplay.
'brass' becomes 'nerve' (synonyms).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'shelved storage' becomes 'racking' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'nerve'+'racking'='NERVE-RACKING'
Can you help me to learn more?
(Other definitions for nerve-racking that I've seen before include "Causing great anxiety" , "Stressful" , "Harrowing" .)