Part of foot that is bearing weight in bike stunt (7)
I believe the answer is:
wheelie
'bike stunt' is the definition.
(I've seen this in another clue)
'part of foot that is bearing weight' is the wordplay.
'part of foot' becomes 'heel' (heel is a part of the foot).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'bearing' says to put letters next to each other.
'weight' becomes 'w' (short for weight).
'heel'+'ie'='heelie'
'heelie' put after 'w' is 'WHEELIE'.
'in' acts as a link.
(Other definitions for wheelie that I've seen before include "Type of bin" , "Bike trick" , "dangerous move on bike?" , "Biking trick" , "good move on bike?" .)