Endangered layer OZONE [not platypus]
Long in the tooth OLD [what you'd have to be to remember that expression]
Nipper's co. RCA [definitely not a puppy]
6-Across suffix ISM [opportune placement]
Two foursomes for OCTET suggests that the latter is composed of two groups of four, but an octet is not by definition divided by sub-groups. Similarly, four duos or eight solos do not comprise an octet.
For TILTS replace
Pinball no-nos with
What a romantic does at windmills.
For TARP replace
Ball field protector with
Baseball cover.
