A course that is purely experimental? (5,3)
I believe the answer is:
trial run
'a course that is purely experimental?' is the definition.
The definition suggests a singular noun which matches the answer.
'course that is purely experimental?' is the wordplay.
I cannot quite understand how this works, but
'course' could be 'run' (synonyms) and 'run' is present in the answer.
'experimental?' could be 'trial' (synonyms) and 'trial' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for trial run that I've seen before include "A test for a car" , "Pilot" , "Practice attempt" , "Turn rail around in practical test" , "test-drive" .)