One beginning to fail (7)
I believe the answer is:
founder
'fail' is the definition.
(I know that founder is a type of fail)
'one beginning' is the wordplay.
I cannot really see how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is present in the answer.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for founder that I've seen before include "Sink, come to grief" , "Institution's former" , "Capsize, being an originator" , "One who establishes an institution" , "(Of ship) fill with water and sink" .)