Angry as a deserter? (5)
I believe the answer is:
ratty
'angry' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for ratty that I've seen before include "water vole, literally" , "Characteristic of pest" , "Irritable, peevish" , "Wretched" , "Short" .)