Informed about English National Front showing large increase (7)
I believe the answer is:
tenfold
'showing large increase' is the definition.
(multiplied by ten)
'informed about english national front' is the wordplay.
'informed' becomes 'told' (telling is a kind of informing).
'about' indicates putting letters inside.
'english national front' becomes 'ENF' (abbreviation).
'told' enclosing 'enf' is 'TENFOLD'.
(Other definitions for tenfold that I've seen before include "(Multiplied) by putting 0 on end" , "several times" , "x10" , "(Increased) by an order of magnitude" , "An order of magnitude as much" .)