Crossword puzzle clue "it's often unaccounted for or a hint to this puzzle's circled letters"

It's often unaccounted for ... or a hint to this puzzle's circled letters

Secret military mission ... or a hint to the circled letters in this puzzle?

"It's on me!" ... or a hint to this puzzle's circled letters

Climactic show ending, and a literal hint to this puzzle's circled letters

Like most pet dogs ... or a hint to this puzzle's circled letters

"Keep this between us" ... or hint to this puzzle's circled letters

Word that can precede each set of circled letters, forming a literal hint for entering certain answers in this puzzle

Pub purchases, and a hint to this puzzle's circled letters