Fixed loose spring (3,4)
I believe the answer is:
set free
'spring' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how one could define the other.
'fixed loose' is the wordplay.
'fixed' becomes 'set' (both can mean decided or determined).
'loose' becomes 'free' (synonyms).
'set'+'free'='SET FREE'
Can you help me to learn more?
(Other definitions for set free that I've seen before include "Released" , "Clear" , "without the box" , "Turn loose" , "no longer detained" .)