Settle with firm, start making contract (10)
I believe the answer is:
compromise
'settle' is the definition.
(compromising is a kind of settling)
'firm start making contract' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'start' suggests taking the first letters.
'contract' becomes 'promise' (I can't justify this - if you can you should believe this answer much more).
The initial letter of 'making' is 'm'.
'co'+'m'+'promise'='COMPROMISE'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for compromise that I've seen before include "Trade-off" , "Give-and-take" , "Settlement" , "accommodation" , "Agree a middle way" .)