Hare-brained sort initially apt to make spiteful remarks (6)
I believe the answer is:
scatty
'hare-brained' is the definition.
(I've seen this before)
'sort initially apt to make spiteful remarks' is the wordplay.
I cannot quite understand how this works, but
'spiteful' could be 'catty' (catty can mean spiteful or nasty) and 'catty' is located in the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for scatty that I've seen before include "Disorganised, unpredictable" , "Not thinking straight" , "Crazy - in jazzy way?" , "Slightly crazy" , "Forgetful and lacking focus" .)