Irritating glitch youngster concealed (5)
I believe the answer is:
itchy
'irritating' is the definition.
(I've seen this before)
'glitch youngster concealed' is the wordplay.
'concealed' indicates a hidden word.
'ITCHY' is hidden within 'glitch youngster'.
(Other definitions for itchy that I've seen before include "Tingling - desirous" , "Like the feet of the restless" , "Needing a scratch" , "Making one want to scratch" , "Irritable" .)