Transport energy proposal (7)
I believe the answer is:
emotion
'transport' is the definition.
('transport' can refer to an overwhelming emotion)
'energy proposal' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'proposal' becomes 'motion' (motion is a kind of proposal).
'e'+'motion'='EMOTION'
(Other definitions for emotion that I've seen before include "Agitation of mind" , "A strong instinctive feeling" , "Passion" , "E.g. fear, hate etc." , "Strong feeling, love or jealousy" .)