It may occur at any time (4)
I believe the answer is:
idea
'it may occur at any time' is the definition.
The definition suggests a singular noun which matches the answer.
'it' is the wordplay.
I cannot quite see how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found in the answer.
The remaining letters 'ida' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for idea that I've seen before include "Purpose" , "Notion, belief" , "Product of the mind" , "Creative spark" , "Thought or notion (4)" .)