Pay to carry on (4)
I believe the answer is:
wage
I believe this is a double definition.
'pay' is the first definition.
(I know that pay can be written as wage)
'carry on' is the second definition.
(as in waging war)
'to' acts as a link.
(Other definitions for wage that I've seen before include "Money earned" , "Carry on - remuneration" , "Regular payment for work" , "Money paid to worker" , "Amount earned" .)