Is a moving one astir? (5)
I believe the answer is:
stair
'is a' is the definition.
I can't judge whether this definition defines the answer.
'moving one astir?' is the wordplay.
'moving' is an anagram indicator.
'astir' anagrammed gives 'STAIR'.
Can you help me to learn more?
(Other definitions for stair that I've seen before include "One of a flight of steps" , "Flight unit" , "Word linking way and well" , "one's seen in flight" , "Support on which to step" .)