Ruby insinuated I resigned to head off such pervasiveness (8)
I believe the answer is:
ubiquity
'pervasiveness' is the definition.
(I've seen this in another clue)
'ruby insinuated i resigned to head off' is the wordplay.
I cannot really see how this works, but
'i' is present in the answer.
'resigned' could be 'quit' (I've seen this in another clue) and 'quit' is found in the answer.
This explanation may well be incorrect...
'such' acts as a link.
Can you help me to learn more?
(Other definitions for ubiquity that I've seen before include "all over the place" , "State of being widespread or everywhere" , "appearing everywhere" , "State of being (or seeming to be) everywhere at once" , "Existence everywhere at the same time" .)