Wide part of foot in instrument of torture (5)
I believe the answer is:
wheel
'instrument of torture' is the definition.
(wheel is a kind of instrument of torture)
'wide part of foot' is the wordplay.
'wide' becomes 'w' (abbreviation e.g. in cricket).
'part of foot' becomes 'heel' (heel is a part of the foot).
'w'+'heel'='WHEEL'
'in' is the link.
(Other definitions for wheel that I've seen before include "Circular frame on axle" , "The first technological invention?" , "Ferris -; Catherine -" , "Circular object (in no need of re-invention!)" , "Turn round quickly" .)