Surrender and send in a proposal (6)
I believe the answer is:
submit
'surrender' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for submit that I've seen before include "Put forward for approval or yield" , "Throw in the towel" , "Yield or refer to another" , "Yield to the control of another" , "Refer for judgement or consideration" .)