Jemmy (7)
I believe the answer is:
crowbar
'jemmy' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for crowbar that I've seen before include "Burglar's tool, perhaps" , "one able to afford purchase" , "Powerful opener" , "Lever used for opening or lifting" , "Tool for breaking and entering" .)