Irritated about exam? (5)
I believe the answer is:
testy
'irritated about exam?' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives occasionally define each other.
'irritated about exam?' is the wordplay.
'irritated' becomes 'y' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'about' says to put letters next to each other.
'exam?' becomes 'test' ('test' can be a synonym of 'exam').
'y' put after 'test' is 'TESTY'.
(Other definitions for testy that I've seen before include "Easily annoyed" , "Short-tempered" , "Irritable" , "bad temper" , "Bad-tempered" .)