Liable to be lying (5)
I believe the answer is:
prone
This clue is a double definition.
'liable' is the first definition.
(both can mean having a tendency for something)
'be lying' is the second definition.
(I've seen this before)
'to' is the link.
(Other definitions for prone that I've seen before include "Liable (to suffer) - lying down" , "Lying face downward" , "Given" , "Recumbent, likely" , "Placed face down" .)