Those watching outside fabricated rest about hag (9)
I believe the answer is:
twitchers
'those watching outside' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'fabricated rest about hag' is the wordplay.
'fabricated' indicates an anagram.
'about' means one lot of letters goes inside another.
'hag' becomes 'witch' (synonyms).
'rest' anagrammed gives 'ters'.
'ters' enclosing 'witch' is 'TWITCHERS'.
Can you help me to learn more?
(Other definitions for twitchers that I've seen before include "unsettled people" , "Naturalists" .)