Test shaft beneath rising chopper (7)
I believe the answer is:
examine
'test' is the definition.
(I know that test can be written as examine)
'shaft beneath rising chopper' is the wordplay.
'shaft' becomes 'mine'.
'beneath' says to put letters next to each other (in a down clue).
'rising' is a reversal indicator (going up in a down clue).
'chopper' becomes 'axe' (something which chops).
'axe' back-to-front is 'exa'.
'mine' put after 'exa' is 'EXAMINE'.
(Other definitions for examine that I've seen before include "Investigate" , "Inspect; question in court" , "Question (a witness)" , "Test, probe" , "Subject to inspection" .)