Lifelong shoemaker, so devoted? (2,3,4)
I believe the answer is:
to the last
'lifelong shoemaker' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'so devoted?' is the wordplay.
I cannot really understand how this works, but
'so' could be 'as' (eg 'not as tall as me' means 'not so tall as me') and 'as' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for to the last that I've seen before include "Until death" , "Back to work, Hans Sachs" , "till you die!" , "Presumably a rallying call to encourage cobbler" .)