Relinquished set (4,4)
I believe the answer is:
laid down
'relinquished set' is the definition.
Although both the answer and definition are past participle verbs, I cannot understand how one could define the other.
'relinquished set' is the wordplay.
'relinquished' becomes 'laid' (I am not sure about this - if you are sure you should believe this answer much more).
'set' becomes 'down' ('down' can be similar in meaning to 'set').
'laid'+'down'='LAID DOWN'
Can you help me to learn more?
(Other definitions for laid down that I've seen before include "specified" , "Insisted upon - abandoned" , "Ordained" , "Stipulated - deposited" .)