Ubiquitous old politician with grudge about Islington area (11)
I believe the answer is:
omnipresent
'ubiquitous' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for omnipresent that I've seen before include "Everywhere at the same time" , "travelling all over the place" , "Existing everywhere" , "Encountered everywhere" , "Found everywhere" .)