Dad backing mum perhaps is obvious (8)
I believe the answer is:
apparent
'is obvious' is the definition.
(similar in meaning)
'dad backing mum' is the wordplay.
'dad' becomes 'pa' (both can mean one's father).
'backing' shows that the letters should be reversed in order.
'mum' becomes 'parent'.
'pa' backwards is 'ap'.
'ap'+'parent'='APPARENT'
'perhaps' acts as a link.
(Other definitions for apparent that I've seen before include "Obvious; seemingly true" , "Readily perceived" , "as such an heir" , "Seeming real or true" , "Seeming true; obvious" .)