When father returned by himself, the rift was obvious (8)
I believe the answer is:
apparent
'obvious' is the definition.
(similar in meaning)
'when father returned by' is the wordplay.
'when' becomes 'parent' (I can't explain this - if you can you should give a lot more credence to this answer).
'father' becomes 'pa' (pa can mean dad or father).
'returned' shows that the letters should be reversed in order.
'by' is a charade indicator (letters next to each other).
'pa' back-to-front is 'ap'.
'parent' put after 'ap' is 'APPARENT'.
'himself the rift was' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for apparent that I've seen before include "Readily perceived" , "Obvious; seeming real" , "Quite obvious and clear" , "Obvious, evident" , "See 1" .)