More than one feeling stressed at heart about proposal (8)
I believe the answer is:
emotions
'more than one feeling' is the definition.
(emotion is a kind of feeling)
'stressed at heart about proposal' is the wordplay.
'at heart' means to look at the middle letters.
'about' indicates putting letters inside.
'proposal' becomes 'motion' (proposal at a meeting).
The middle letters of 'stressed' are 'es'.
'es' placed around 'motion' is 'EMOTIONS'.
(Other definitions for emotions that I've seen before include "Passions" , "Anger and love, say" , "Strong feelings" , "instinctive feelings" , "Intense mental feelings, like love or hate" .)