Is it flounder?

Reposted:

Entrance principally staged (ibid.) ultimately welcomed by Chevron (9)

Clues:

Entrance principally staged (ibid.) ultimately welcomed by Chevron (9)

_ e _ _ _ _ _ _ e

There’s a containment indicator.

The 3-word section that goes into the container has another type of indicator applied.

EDIT: Once you know what the other indicator is and how it applies to the 3 words, it will all make sense - especially when it goes into the container.

No, mesmerise isn’t the answer.

Entrance principally staged (ibid.) ultimately welcomed by Chevron (9)

_ e _ _ _ _ _ l e   (Lower-case L, not capital i)

There’s a containment indicator.

The 3-word section that goes into the container has another type of indicator applied. EXTRA: if i told you what sort of indicator that is, it would give away the answer.

ADDITIONAL: The fact that it applies to three words is the first thing you need to keep in mind.