Frightful bores, sedate and rational (5)

I believe the answer is:

sober

'sedate and rational' is the definition.
(sober can mean sensible or level-headed)

'frightful bores' is the wordplay.
'frightful' indicates an anagram (a frightful spelling).
'bores' with letters rearranged gives 'SOBER'.

(Other definitions for sober that I've seen before include "Serious, thoughtful" , "Sensible - clear-headed" , "Dignified -- lacking colour" , "Serious, dull" , "Teetotal" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.