Supposed weather forecaster at first skulking indoors (7)
I believe the answer is:
swithin
'supposed weather forecaster' is the definition.
The definition suggests a singular noun which matches the answer.
'at first skulking indoors' is the wordplay.
'at' says to put letters next to each other.
'first skulking' becomes 's' (1st letter of 'skulking').
'indoors' becomes 'within' (I've seen this before).
's' next to 'within' is 'SWITHIN'.
Can you help me to learn more?
(Other definitions for swithin that I've seen before include "Saint; with sin (anag,)" , "Saint associated with weather (I not U)" .)