Mature reflection leads to half the side being given release (12)
I believe the answer is:
deliberation
'mature reflection leads to half' is the definition.
I can't judge whether this definition defines the answer.
'side being given release' is the wordplay.
'side being given' becomes 'de' (I can't explain this - if you can you should give a lot more credence to this answer).
'release' becomes 'liberation' (synonyms).
'de'+'liberation'='DELIBERATION'
'the' is the link.
Can you help me to learn more?
(Other definitions for deliberation that I've seen before include "Careful thought" , "Considering" , "circumspection?" , "thought required" , "Study" .)