Draw a line under the law? (4)
I believe the answer is:
rule
'the law?' is the definition.
(law is a kind of rule)
'draw a line under' is the wordplay.
I cannot really understand how this works, but
'line' could be 'l' (used when specifying particular lines from a poem) and 'l' is found in the answer.
The remaining letters 'rue' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rule that I've seen before include "Determination" , "line to be followed" , "Strip" , "Exercise authority over" , "Standard" .)