Clue: Ideal according to splinter group caught by some (10)
Answer: PERFECTION
Explanation: Ideal according to splinter group caught by some (10) 
PER + FECTION (homophone, supposedly, of FACTION).
 
Even with the qualifying "for some", I struggle with FECTION as a homophone fo FACTION, but then as a Scot, I hate a lot of homophone clues.