's head of printing excitedly secures [Grazia InStyle] 's core territory (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

( Anagram of [excitedly] GRAZIA and P [ first letter of {head of} P rinting]) containing (secures) ST ( letters within [core] in ST yle) – usually ‘core’ refers to the middle letters, but not in this case