Colour proposal — is not keen initially (4)
I believe the answer is:
pink
'colour' is the definition.
(pink is a kind of colour)
'proposal is not keen initially' is the wordplay.
'initially' suggests taking the first letters.
The first letters of 'proposal is not keen' is 'PINK'.
(Other definitions for pink that I've seen before include "(Shade of) flower" , "Cut wavy edge on, plant" , "Ros colour" , "Colour; garden plant" , "... similar flower - colour" .)