Be liable to shrink (8)
I believe the answer is:
contract
'to shrink' is the definition.
(I know this)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for contract that I've seen before include "Agreement - lessen" , "type of bridge" , "Undertake" , "Promise" , "Agree - reduce" .)