Against opening course originally? Only a bit (7)
I believe the answer is:
soupcon
'bit' is the definition.
(I've seen this in another clue)
'against opening course originally? only a' is the wordplay.
I cannot really understand how this works, but
'against' could be 'con' (as in pros and cons) and 'con' is present in the answer.
'course' could be 'soup' (I've seen this before) and 'soup' is found 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 soupcon that I've seen before include "Smidgen" , "Hint" , "Dash" , "Very tiny amount" , "very little" .)