Decided to repair bottom of shoe split by tips of umpteen tacks (8)
I believe the answer is:
resolute
'decided' is the definition.
(I've seen this before)
'repair bottom of shoe split by tips of umpteen tacks' is the wordplay.
'repair' becomes 're' (I am not sure about this - if you are sure you should believe this answer much more).
'bottom of shoe' becomes 'sole'.
'split by' is an insertion indicator.
'tips of' indicates taking the first letters (I've seen 'tip of' mean this).
The initial letters of 'umpteen tacks' is 'ut'.
'sole' enclosing 'ut' is 'solute'.
're'+'solute'='RESOLUTE'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for resolute that I've seen before include "Firm in purpose" , "'Firm, unhesitating (8)'" , "Firmly determined" , "Determined, unwavering" , "Showing great determination, fully committed" .)