The most common and most likely answer to this crossword clue is the 8 letter word MUGSHOTS
I've seen this crossword clue in Independent
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More clues leading to the result MUGSHOTS
Buddy explains!

The straight part
We know that "portraits" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case portraits = mugshots.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 MUGSHOTS mean?
MUGSHOTS noun- A photograph taken of the head and shoulders, often from the front and in profile, usually taken in conjunction with somebody's arrest.
- An unflattering photograph of a person's face.