Easy to understand dad backing mum? (8)
I believe the answer is:
apparent
'easy to understand' is the definition.
(apparent can mean obvious or evident)
'dad backing mum?' is the wordplay.
'dad' becomes 'pa' (synonyms).
'backing' says the letters should be written backwards.
'mum?' becomes 'parent' (mum is a kind of parent).
'pa' reversed gives 'ap'.
'ap'+'parent'='APPARENT'
(Other definitions for apparent that I've seen before include "Seeming to be but not necessarily so" , "Noticeable" , "Readily perceived" , "Evident, manifest" , "Visible - plain - presumable" .)