Angry at having a disastrous try-out! (5)
I believe the answer is:
ratty
'angry' is the definition.
(thesaurus)
'having a disastrous try-out' is the wordplay.
'having' becomes 'at' (I am not sure about this - if you are sure you should believe this answer much more).
'a disastrous' is an anagram indicator.
'out' indicates putting letters inside.
'try' anagrammed gives 'rty'.
'at' going into 'rty' is 'RATTY'.
'at' acts as a link.
Can you help me to learn more?
(Other definitions for ratty that I've seen before include "Bad-tempered, irritable as a rodent" , "his friend being a dangerous driver" , "Mole's friend (The Wind in the Willows)" , "Characteristic of pest" , "describing vermin" .)