Engineer making contribution to Mariotte's law (5)
I believe the answer is:
tesla
'engineer' is the definition.
(I know that Tesla is a electrical engineer)
'contribution to mariotte's law' is the wordplay.
'contribution to' indicates the answer is hidden within the clue.
'TESLA' can be found hidden inside 'mariottes law'.
'making' acts as a link.
(Other definitions for tesla that I've seen before include "SI unit; steal (anag.)" , "Unit of magnetic flux density" , "Physicist" , "Nikola ---, electricity pioneer" , "Inventor" .)