Amused somehow about son being adopted (7)
I believe the answer is:
assumed
'being adopted' is the definition.
(I've seen this before)
'amused somehow about son' is the wordplay.
'somehow' indicates an anagram.
'about' indicates putting letters inside.
'son' becomes 's'.
'amused' with letters rearranged gives 'asumed'.
'asumed' enclosing 's' is 'ASSUMED'.
(Other definitions for assumed that I've seen before include "Falsely adopted" , "Took (responsibility)" , "False" , "Put it on - without being told?" , "Surmised" .)