Forbidding being home when relative is coming round (8)
I believe the answer is:
sinister
'forbidding' is the definition.
(synonyms)
'home when relative is coming round' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'when relative' becomes 'sister' (sister is a kind of relative. I am not sure about the 'when' bit.).
'is coming round' is an insertion indicator.
'in' placed into 'sister' is 'SINISTER'.
'being' is the link.
Can you help me to learn more?
(Other definitions for sinister that I've seen before include "not right!" , "Malign, ominous" , "Very unpleasant" , "can be injurious" , "Suggestive of evil, threatening harm" .)