Not working is quite irregular (3,2,5)
I believe the answer is:
out of order
This clue could be a double definition.
'not working' is the first definition.
(I've seen this in another clue)
'quite irregular' is the second definition.
'out of order' can be an answer for 'irregular' (I've seen this before). I am not certain of the 'quite' bit.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for out of order that I've seen before include "unusually arranged" , "(Mechanism) broken" , "Disgraced knight might be told to get this" , "Bust - behaving badly" , "Not in religious community" .)