Characters within cell revolutionised record number of countries (6)
I believe the answer is:
europe
'countries' is the definition.
(I have seen 'several countries' mean 'europe' so perhaps 'countries' could also mean 'europe')
'characters within cell revolutionised record number' is the wordplay.
'characters within' means to look at the middle letters.
'cell' becomes 'fuel cell' (fuel cell is a kind of cell).
'revolutionised' says the letters should be written backwards.
'record number' becomes 'rope' (I can't justify this - if you can you should believe this answer much more).
The central letters of 'fuel' are 'ue'.
'ue' reversed gives 'eu'.
'eu'+'rope'='EUROPE'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for europe that I've seen before include "Land mass from the Atlantic to the Urals" , "Second smallest continent" , "Did Poe rue being on the continent?" , "lot of countries" , "Our near continent?" .)