There is no 7-letter anagram for RRTIENE. The longest word is "renter."
If an additional A is available, you can spell the 8-letter word retainer.
The letters spell the word casino.
The letters spell the word "freelance."
The letters spell the word geometrical.
The letters APTRUSIS spell the word "upstairs."
Those letters will spell the word vinegar.
The letters can spell the word publications (or No, a publicist!).
These letters unscramble to spell the word herbal.
The letters spell 'broccoli'.
The letters spell weary.
The letters spell the word temples.
The letters spell the word obstruct.
The letters spell the word "mineralogist" (rock scientist).