Mechanic showing skill if joined by decorator (9)
I believe the answer is:
artificer
'mechanic' is the definition.
(I've seen this before)
'skill if joined by decorator' is the wordplay.
'skill' becomes 'art' (both can mean a talent).
'joined by' is a charade indicator (letters next to each other).
'decorator' becomes 'icer' (some decorating a cake with icing).
'art'+'if'+'icer'='ARTIFICER'
'showing' is the link.
(Other definitions for artificer that I've seen before include "One into skill" , "Skilled worker" , "Skilled mechanic" , "Inventor who's skilful" , "Mechanic in the army or navy" .)