Take as one's own (5)
'take as one's own' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for adopt that I've seen before include "Choose as one's own" , "Embrace" , "Formally approve" , "Accept as one's own" , "make one's own" .)
(Another definition for coopt that I've seen is " Appropriate".)