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'm not certain of the 'shoe's' bit.
'undersurface in to be repaired' is the wordplay.
'undersurface' becomes 'sole' (sole is a kind of undersurface).
'in' means one lot of letters goes inside another.
'repaired' indicates an anagram.
'to'+'be'='tobe'
'tobe' anagrammed gives 'obte'.
'sole' placed 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(Other definitions for obsolete that I've seen before include "'No longer used, out of date (8)'" , "No longer current" , "Out-of-date" , "Antiquated" , "No longer useful" .)