Transport proposal EU leader leads (7)
I believe the answer is:
emotion
'transport' is the definition.
('transport' can refer to an overwhelming emotion)
'proposal eu leader leads' is the wordplay.
'proposal' becomes 'motion' (proposal at a meeting).
'leader' suggests taking the first letters.
'leads' means one lot of letters go next to another (some letters go in front of others).
The first letter of 'eu' is 'e'.
'motion' put after 'e' is 'EMOTION'.
(Other definitions for emotion that I've seen before include "Feeling such as joy, sorrow and fear" , "Intense feeling" , "Feeling like love or hate" , "A strong instinctive feeling" , "Strong feeling of joy, fear etc" .)