Senior nurse seen around at home -- that's ominous (8)
I believe the answer is:
sinister
'ominous' is the definition.
('sinister' can be a synonym of 'ominous')
'senior nurse seen around at home' is the wordplay.
'senior nurse' becomes 'sister' (I've seen this before).
'seen around' indicates putting letters inside.
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'sister' going around 'in' is 'SINISTER'.
'that's' acts as a link.
(Other definitions for sinister that I've seen before include "Forbidding" , "Threatening; evil-looking" , "On the left (of shield) (her.); wicked, criminal" , "Suggestive of evil/harm" , "Very unpleasant" .)