Distressed when what's been negotiated doesn't begin to encompass proposal (9)
I believe the answer is:
emotional
'distressed when what's been negotiated doesn't' is the definition.
I can't tell whether this definition defines the answer.
'begin to encompass proposal' is the wordplay.
'begin' becomes 'eal' (I can't justify this - if you can you should give a lot more credence to this answer).
'to encompass' indicates putting letters inside (I've seen this in other clues).
'proposal' becomes 'motion' (proposal at a meeting).
'eal' enclosing 'motion' is 'EMOTIONAL'.
Can you help me to learn more?
(Other definitions for emotional that I've seen before include "Exhibiting strong feelings" , "showing passion" , "Impassioned - excitable" , "Loving" , "Poignant" .)