Almost fall over in proper second test (7)
I believe the answer is:
retrial
'second test' is the definition.
(a second trial or test)
'almost fall over in proper' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'fall over' becomes 'trip' (I've seen this in another clue).
'in' means one lot of letters goes inside another.
'proper' becomes 'real' (similar in meaning).
'trip' with its final letter taken off is 'tri'.
'tri' going within 'real' is 'RETRIAL'.
(Other definitions for retrial that I've seen before include "test, after failure in first" , "Second court hearing" , "Further action" , "Revived case" , "Hearing repeat" .)