Become liable for (5)
I believe the answer is:
incur
'become liable for' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for incur that I've seen before include "Become subject to (something unpleasant)" , "Bring on oneself, probably unpleasant" , "Meet" , "Bring something unpleasant on oneself (5)" , "Bring on as a consequence" .)