RUN up, as debts (10)
'run up as debts' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for incur that I've seen before include "Bring on oneself, say costs" , "Fall into - invite" , "Invite, bring about" , "Meet" , "Become subject to (penalty)" .)
(Another definition for accumulate that I've seen is " Amass".)