Participants trade in currency and become subject to something unpleasant (5)
I believe the answer is:
incur
'participants trade' is the definition.
The answer and definition can be both to do with fundamental existence as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'in currency and become subject to something unpleasant' is the wordplay.
I cannot really understand how this works, but
'in' is found in the answer.
The remaining letters 'cur' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for incur that I've seen before include "Fall into - invite" , "Become liable or subject to" , "Become responsible for" , "To become liable to, suffer" , "Risk" .)