Bad omens from rector in powerful sermon's introduction (8)
I believe the answer is:
portents
'bad omens' is the definition.
'portents' can be an answer for 'omens' ('portent' can be a synonym of 'omen'). I am not sure about the 'bad' bit.
'rector in powerful sermon's introduction' is the wordplay.
'rector' becomes 'r'.
'in' is an insertion indicator.
'powerful' becomes 'potent' (synonyms).
'sermon's introduction' becomes 's' (I can't explain this - if you can you should give a lot more credence to this answer).
'r' inserted into 'potent' is 'portent'.
'portent'+'s'='PORTENTS'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for portents that I've seen before include "Signs of things about to happen" , "Ominous signs" , "Omens" .)