Given it, one is somewhat liable to return (4)
I believe the answer is:
bail
'given it' is the definition.
I can't judge whether this definition defines the answer.
'one is somewhat liable to return' is the wordplay.
'one' becomes 'li' (I've seen this in other clues).
'is somewhat liable' becomes 'ab' (I can't justify this - if you can you should give a lot more credence to this answer).
'to return' shows that the letters should be reversed in order.
'li'+'ab'='liab'
'liab' written backwards gives 'BAIL'.
Can you help me to learn more?
(Other definitions for bail that I've seen before include "Money paid for temporary release" , "Partition in stable" , "Sum of money guaranteeing the accused's return to court" , "Remove water from -- part of wicket" , "Money lodged to secure release pending trial" .)