Refrain from warning attempt (6)
I believe the answer is:
forego
'refrain' 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 you can see a link between them that I can't see?
'warning attempt' is the wordplay.
'warning' becomes 'fore' (used to warn of airborne balls on a golf course).
'attempt' becomes 'go' (go is a kind of attempt).
'fore'+'go'='FOREGO'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for forego that I've seen before include "Go without, give up" , "Surrender" , "Manage without" , "Relinquish - do without" , "Go without (desirable thing)" .)