Romans upset by a demand for cash (6)
I believe the answer is:
ransom
'a demand for cash' is the definition.
I can't tell whether this definition defines the answer.
'romans upset' is the wordplay.
'upset' indicates anagramming the letters.
'romans' with letters rearranged gives 'RANSOM'.
'by' is the link.
Can you help me to learn more?
(Other definitions for ransom that I've seen before include "Money paid for release of a hostage" , "Redeem" , "Money demand" , "Freedom payment" , "Money to get a hostage released" .)