The most common and most likely answer to this crossword clue is the 8 letter word VALKYRIE
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The straight part
We know that "stiff escort" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stiff escort = valkyrie.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does VALKYRIE mean?
VALKYRIE noun- Any of the female attendants of Odin, figures said to guide fallen warriors from the battlefield to Valhalla.