Antiquated shoe's undersurface in to be repaired (8)
I believe the answer is:
obsolete
'antiquated shoe's' is the definition.
'obsolete' can be an answer for 'antiquated' (I've seen this before). I am not sure about the 'shoe's' bit.
'undersurface in to be repaired' is the wordplay.
'undersurface' becomes 'sole' (sole is a kind of undersurface).
'in' indicates putting letters inside.
'repaired' indicates anagramming the letters.
'to'+'be'='tobe'
'tobe' anagrammed gives 'obte'.
'sole' put within 'obte' is 'OBSOLETE'.
Can you help me to learn more?
(Other definitions for obsolete that I've seen before include "'No longer used, out of date (8)'" , "No longer current" , "Out-of-date" , "Antiquated" , "No longer useful" .)