General principle, one applied to the largest numbers (6)
I believe the answer is:
maxima
'the largest numbers' is the definition.
(I've seen this before)
'general principle one applied to' is the wordplay.
'general principle' becomes 'maxim' (I've seen this before).
'one' becomes 'a'.
'applied to' is a charade indicator (letters next to each other).
'maxim'+'a'='MAXIMA'
(Other definitions for maxima that I've seen before include "Highest points" , "Largest numbers" , "greatest possible amounts" , "upper limits)" , "extremely high values" .)