A tin recycled in cunning mechanical device (10)
I believe the answer is:
cantilever
'mechanical device' is the definition.
(mechanical part)
'a tin recycled in cunning' is the wordplay.
'recycled' is an anagram indicator.
'in' is an insertion indicator.
'cunning' becomes 'clever' (synonyms).
'a'+'tin'='atin'
'atin' anagrammed gives 'anti'.
'anti' inserted inside 'clever' is 'CANTILEVER'.
(Other definitions for cantilever that I've seen before include "bridge design" , "Projecting mass" , "Projecting beam fixed at one end" , "Beam supported at only one end" , "support at one end" .)