Still lacking a proposal (10)
I believe the answer is:
motionless
'still' is the definition.
(I know that still can be written as motionless)
'lacking a proposal' is the wordplay.
I cannot really see how this works, but
'lacking' could be 'less' (I've seen this in another clue) and 'less' is located in the answer.
'proposal' could be 'motion' (proposal at a meeting) and 'motion' is found within the answer.
No letters remain.
This explanation may well be incorrect...
(Other definitions for motionless that I've seen before include "Inert" , "Perfectly still" , "constipated?" , "not having anything to vote about?" , "Immobile" .)