Tests part of complex Amstrad
I believe the answer is:
exams
'tests' is the definition.
('exam' can be a synonym of 'test')
'part of complex amstrad' is the wordplay.
'part of' indicates a hidden word.
'EXAMS' is hidden within 'complex amstrad'.
(Other definitions for exams that I've seen before include "GCSE, A-level, etc" , "Tests for students" , "summer term commitment?" , "Tests, in short" , "finals?" .)