Walter has something on hand to the very end (5)

'walter' is the definition.
(main character in The Secret Life of Walter Mitty)

'something on hand to the very end' is the wordplay.
'something' becomes 'it' (both can refer to an object).
'on' indicates putting letters inside.
'hand' becomes 'mt' (I can't explain this - if you can you should believe this answer much more).
'to' says to put letters next to each other.
'end' indicates one should take the final letters.
The final letter of 'very' is 'y'.
'it' placed inside 'mt' is 'mitt'.
'mitt'+'y'='MITTY'

'has' is the link.

Can you help me to learn more?