Walk most of the way back, as a rule (3)
I believe the answer is:
law
'a rule' is the definition.
(law is a kind of rule)
'walk most of the way back' is the wordplay.
'walk' becomes 'l' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'most of' means to remove the last letter.
'back' says the letters should be written backwards.
'way' with its final letter taken off is 'wa'.
'wa' in reverse letter order is 'aw'.
'l'+'aw'='LAW'
'as' is the link.
Can you help me to learn more?
(Other definitions for law that I've seen before include "'Possession is nine points of the ...'" , "Official rule" , "Rule of conduct" , "Set of rules laid down by authority" , "Collection of rules imposed by authority" .)