Regularly trying machinery (3)
I believe the answer is:
rig
'machinery' is the definition.
(thesaurus)
'regularly trying' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'trying' are 'RIG'.
(Other definitions for rig that I've seen before include "engineer or > doctor" , "Manage or control fraudulently, say an election" , "Manipulate (result)" , "Oil derrick" , "Arrangement of masts, spars and sails on a ship" .)