Clear a mum or dad to adopt Penny (8)
I believe the answer is:
apparent
'clear' is the definition.
('apparent' can be a synonym of 'clear')
'a mum or dad to adopt penny' is the wordplay.
'mum or dad' becomes 'parent' (I've seen this before).
'to adopt' means one lot of letters goes inside another.
'penny' becomes 'p'.
'parent' placed around 'p' is 'pparent'.
'a'+'pparent'='APPARENT'
(Other definitions for apparent that I've seen before include "Writ large" , "Seeming to be but not necessarily so" , "Evident or seeming to be" , "Noticeable" , "Readily perceived" .)