Prosthesis setter's placed at front of factory (7)
I believe the answer is:
implant
'prosthesis' is the definition.
(implant is a kind of prosthesis)
'setter's placed at front of factory' is the wordplay.
I cannot really understand how this works, but
'setter's' could be 'im' (referring to the crossword setter) and 'im' is found in the answer.
'factory' could be 'plant' (a manufacturing plant) and 'plant' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for implant that I've seen before include "Insert or fix into the body" , "New element in trap" , "Fix securely and deeply" , "Introduce" , "get fixed" .)