Instructor’s shoe (7)
I believe the answer is:
trainer
I believe this clue is a double definition.
'instructor's' is the first definition.
(thesaurus)
'shoe' is the second definition.
(I've seen this before)
(Other definitions for trainer that I've seen before include "He assists athlete to become fit" , "Casual shoe" , "teacher" , "Terrain (anag.)" , "Casual 11 ac" .)