Mechanical device skinned fantasy author (7)
I believe the answer is:
ratchet
'mechanical device' is the definition.
(ratchet is a kind of mechanical device)
'skinned fantasy author' is the wordplay.
'skinned' indicates the central letters.
'fantasy author' becomes 'Pratchett' (fantasy author Terry Pratchett).
The centre of 'pratchett' is 'RATCHET'.
(Other definitions for ratchet that I've seen before include "Device stopping backward movement" , "Chatter (anag)" , "Device allowing motion in one direction only" , "Set of teeth" , "Device preventing turning backwards" .)