Show the action of a lever (6)
I believe the answer is:
reveal
'show' is the definition.
(revealing is a kind of showing)
'action of a lever' is the wordplay.
'action of' indicates anagramming the letters (I've seen 'action' mean this).
'a'+'lever'='alever'
'alever' is an anagram of 'REVEAL'.
'the' acts as a link.
(Other definitions for reveal that I've seen before include "Divulge; make visible" , "Disclose, make apparent" , "Remove cover or expose to view" , "Remove cover, unveil" , "Remove cover to display" .)