Tests, assuming one works, all right (12)
I believe the answer is:
satisfactory
'all right' is the definition.
('satisfactory' can be similar in meaning to 'all right')
'tests assuming one works' is the wordplay.
'tests' becomes 'sats' (exams taken in UK schools).
'assuming' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'works' becomes 'factory' (factory is a kind of works**).
'sats' enclosing 'i' is 'satis'.
'satis'+'factory'='SATISFACTORY'
(Other definitions for satisfactory that I've seen before include "unexceptional" , "Good enough" , "Acceptable - adequate" , "OK" , "Fulfilling expectations" .)