Chosen but not fully adopted (5)
I believe the answer is:
opted
'chosen' is the definition.
Both the answer and definition are past participle verbs.
Maybe you can see an association between them that I can't see?
'not fully adopted' is the wordplay.
'OPTED' is hidden within the letters.
But, I'm not sure how the hidden word is indicated.
'but' is the link.
Can you help me to learn more?
(Other definitions for opted that I've seen before include "'Decided on, chose (5)'" , "Selected from depot" , "Chose from depot" , "Decided as in 10 Across" , "Chosen - elected" .)