999p ÷ @1 causing irritability? (10)
I believe the answer is:
impatience
'irritability?' is the definition.
(I've seen this before)
'999p 1' is the wordplay.
I cannot really understand how this works, but
'999p' could be 'p' and 'p' is found in the answer.
'1' could be 'i' (Roman numeral) and 'i' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'causing' is the link.
Can you help me to learn more?
(Other definitions for impatience that I've seen before include "Irritation at delay" , "Restlessness" , "irritability" , "embodying intolerance" , "agitation" .)