Asparagus, say, could give one a stabbing pain (5)
I believe the answer is:
spear
'asparagus say' is the definition.
The definition and answer can be both to do with fundamental existence as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?
'one a stabbing pain' is the wordplay.
I cannot really see how this works, but
'one' could be 'a' (a thing is one thing) and 'a' is found in the answer.
'a' could be 'per' (eg 'one a day' means 'one per day') and 'per' is found within the remaining letters.
A single letter 's' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'could give' acts as a link.
Can you help me to learn more?
(Other definitions for spear that I've seen before include "Weapon; asparagus stem" , "Lance" , "Sharp weapon" , "Primitive weapon" , "Asparagus shoot" .)