Tested chopper on the rise, likely to explode? (8)
I believe the answer is:
examined
'tested' is the definition.
('examine' can be a synonym of 'test')
'chopper on the rise likely to explode?' is the wordplay.
'chopper' becomes 'axe' (I've seen this before).
'on the rise' says the letters should be written backwards.
'likely to explode?' becomes 'mined'.
'axe' reversed gives 'exa'.
'exa'+'mined'='EXAMINED'
(Other definitions for examined that I've seen before include "Looked into something closely" , "Questioned closely" , "Tested or scrutinised" , "Questioned, tested" , "Observed and checked out" .)